Openness adds costs to the development and support and it could potentially wreak havoc on the licenses and agreements that Apple has with the current content providers.
So Apple can somehow resolve that havoc with that same itunes content flowing to Macs and iphones and ipods, but they just can't make it work with

TV???
My counter to your suggestions about adding support for DVR and Blu-ray is the following.
You want Blu-ray? Go out a buy a cheap Blu-ray player from Samsung or alike.
You want a DVR? Get one from your cable or satellite TV company. TiVo is the only other major player in this field...
Exactly, so I'm a mass market buyer and I want to buy a bit of hardware to hook to my new HDTV this year. I can buy a BD player which will max out what my TV can show, or I can buy a Tivo which will give me an elegant, effortless way to record a bunch of "free" shows that I really like, or I can buy an

TV which won't give me the 1080i or 1080p quality of that BD player (so it won't max out the quality of picture on my set) and I won't be able to do anything with the programming already flowing into my house via my cable or satt system, instead having to rebuy or re-rent that same content via iTunes if I want to approximate the experience of that Tivo. On which shall I spend that money this year?
Your recommendations are exactly what the mass market is doing. Only instead of adding a BD player or a DVR to an

TV, they are choosing to just buy the BD player and/or the DVR, saving the

TV as a possible future purchase. Apple gets to sell them NO

TV itunes content if they don't get that

TV into their hardware setup. And if enough people choose the BD and/or DVR box(es) instead of

TV, it will take that much longer for Apple's discless/dvr-less vision to be realized. After all, once I have that BD player sitting there, there isn't a lot of motivation to go out and buy another little box from Apple that will only give me access to significantly downgraded (handicapped 720p at best) content. And once I have that DVR entrenched in my setup, I'm not going to be that hungry to pay Apple for a device that will then require me to keep paying for that same content I'm able to record now at little to no additional charge beyond my cable or satt bill (and at higher resolution by the way).
I don't blame the "dummies" in the mass market at all for choosing a soon-to-be obsolete disc-based and/or DVR model to pair with their 1080i or 1080p HDTV. THEY get to enjoy highest quality video NOW, and for however long it takes for those of us clinging to the Apple vision to finally be offered the upgrade we know Apple can deliver. While they are watching their favorite movies and shows in 1080p on their 1080p television, we "geniuses" can smugly enjoy our handicapped 720p at best quality that Apple chooses as our limit, knowing that eventually the world will come around to Apple's (and our) right way of consuming such content. Boy, I'm glad I'm in the smart crowd.
In any case, how is Apple (or anyone for that matter) going to support a DVR experience that can beat what can be had with a cable or satellite box? CableCARD seems to be dead --
Elgato has been in business for years selling DVR add-on products for Macs. If they can do it, Apple could too. Or, as I endorse, Apple could just open the next-gen

TV up a bit so that Elgato-like companies could fill that need if they think there is a sufficient market of foolish people who would buy a DVR add-on for an

TV instead of just paying more (via iTunes) for the same content they could record with that DVR add-on.
Besides, most of the highest-rated shows are still coming from the major networks, which are available to much of the masses for free over the air in HD at levels well beyond the finest of iTunes HD offerings. For those that want DVR capabilities who can receive the major networks, a lot of added value would come from just a DVR option for that handful of channels.
Furthermore, iTunes- even the one in that 5+/-year future- seems unlikely to resolve the live sports issue. But a tuner add-on option for an

TV box (which is half of the step to a full DVR option) could bring live sports to that little box from the major local networks FOR FREE.
Such niceties would make that next-gen

TV much more desirable to the masses, so Apple would sell many more of them. Personally, I don't care if they build in a DVR (or DVR open) option or not. But it is easy for me to see that they would likely sell a lot more

TV's if they gave the BUYERS more of what they want, instead of trying to make the BUYERS come around to their vision of how things are going to be.
This thread was started by someone asking about the future of this product. And even that very first post shows a guy wanting a few features that it does not have now (nor can they be added by third parties to this closed system "as is"). Could it have those features? Sure. If it had them- Apple or third party- would Apple sell more

TVs? Absolutely.
Don't add them, or don't make it possible for others to offer them as add ons, and don't sell more

TV's to those willing buyers. It's as simple as that.
In any case, these are among my arguments against adding DVR and Blu-ray support to the Apple TV. Apple should continue to concentrate on downloadable and streaming delivery over the internet
I fully support that Apple doesn't need to build a BD option or DVR option into a next-gen

TV- just build that next-gen open enough so that those people that want those options could buy them as add-on features (much like adding on hardware (like the Elgato DVR option) to the Mac Mini). That way, the price of the next-gen

TV doesn't have to go up, yet it could be a much more compelling bit of AV equipment for the masses.
I also support that since there already is an iTunes, steaming models and so on, Apple should certainly keep focusing on making that as good as it can be. For example, they shouldn't allow Netflix and similar to have any more movies or shows available to stream to BD players with Netflix extensions than

TV players with their iTunes connection.
The convenience of readily-available content via iTunes would always entice the guy who bought the stock

TV and added on a BD and DVR option when getting to watch something he wants to watch via BD would require a trip to the store if he didn't already capture it via the DVR. If Apple poured it on with iTunes content diversity, and if they sold so many

TVs that the studios would be fiercely competing with pricing (driving prices down), iTunes movies could be priced at less than BD movies, iTunes television could be priced at a level that makes cutting the cable or satt cord more acceptable, and so on. Thus, Apple gets to their vision anyway (QUICKER then waiting for the world to magically come around to this way of thinking).
In short, I agree that things seem to be headed where you think Apple is trying to take them. It does look like downloads and internet sourced content is where we are going. But there's a lot of ways to get there. The mass market is only going to buy so many little boxes to sit next to their TVs. Whoever puts the right combination of features in their box such that they entrench in the masses' living rooms will win the living room. Apple could/should be that company. But IMO, clinging to some of what they are clinging to is not going to make it (magically) happen.
Give the buyers more of what they want, and Apple can still get to their envisioned destination. Refuse the market wants, and they may or may not realize that vision. I'm absolutely convinced they could get there- and more quickly- with the former.