I've seen a lot of sketch artists happily use an iPad Pro as a secondary device, but I don't know any pros who use one as their primary. The iPad Pro as a pro device seems generally to be some sort of fever dream, I don't know anyone who has adopted one as their only device for pro work. It's basically treated as a cheap (and good) Cintiq, where real work is still transferred back to the Mac for real Photoshop.
With the iPad Pro not landing with pros, I think you're really jumping ahead of where we are. There are a lot of reasons iOS isn't considered a pro OS beyond Xcode.
And on PCI-E slots... is it generational? A lot of the cutting edge work needs GPUs, or multiple GPUs, and Apple just doesn't exist in that space. If I need a four GPU system for machine learning... where do I get that? I could use external GPUs, but four GPUs might be starting to push what's reasonable. And I also need to change out the GPUs to keep up, which the current Mac Pro fails at.
It's not an old-people-stuck-in-the-mud thing. I know a lot of people who are not... old... who are having to switch to PCs so they can get their GPUs back.
I mean, even if you're coming out of high school or college and you want to play with machine learning or VR, or even some more intense video editing, the iPad Pro is nowhere. It doesn't do high end graphics. It doesn't do high end CPU work. There are no mid or high end video editors. You can't even plug the iPad into an external display.
For pro workflows, the iPad Pro is nowhere and the MacBook Pro is still the introductory machine.
How much of that is the typical use case, even for a "Pro" users. I think you want to define "Pro" with a very narrow interpretation. Apple doesn't offer me what I need anymore for some of my work, and I've switched to Linux as my utility OS, yet I still find it a lot easier to use OS X as my build env for most of my work.
Do I think Apple is missing the mark with the Mac Pro, yes, and OS X doesn't have API's from some of the stuff I need to do with my Tower. I just don't think Apple should be trying to reinvent the wheel when it comes to the desktop form factor, it is tried and true, but that wasn't the point I was trying to address.
The point I was trying to get across was it's a changing landscape, most people are doing most of there computing on handhelds.
Does it fit every use case, no, but lets see you put your Mac Pro or ATX PC in your pocket with 8 hrs of battery life.
Already we are seeing remote rendering farms, things will move more and more to the cloud. Most people just won't need high power CPU's and GPU's with tons of ram and storage.
Even for gaming, I played around with VirtualGL and Quake III on my Nokia 770. Basically it renders everything on the server, and you run a remote X session, then it compresses the rendered frames to JPEG, sends them over the network, and displays them in you X session.
It worked great, and that was 13 years ago.
I could see, one day, game rendering farms sending compressed images direct to smart tv's with simple input devices. No need to buy the game, download it, buy a CPU and graphics card capable of running it. All that happens on the remote server, all you local terminal does is decompress and display the images, and direct the user input.
We have cameras that upload to the cloud, you can edit in the cloud. Maybe there are even some musical interments that can upload t the cloud. Is this stuff ready for prime time, likely not for many high end photo, video, and audio work, bit that's just matter of bandwidth, really, and bandwidth gets faster everyday.
There are some UI problems to overcome with the iOS when it comes to doing a lot of "Pro" work, however doesn't the iPad Pro support a Keyboard, couldn't support any HID device?
Apple is just going where the most users are, we can't really blame them for that, but lets not pretend that this can't pay dividends down the road, that people that make money with iPad's and iPhones are not "Pro" users, and they are not using "Computers".
We saw this same thing with the mass migration from the desktop to the laptop, did some users still need the desktop, yes, but Apple was making a lot more money with laptops.
In a way, I think Apple is missing the mark, in that they have the cash to throw at the Mac brand, and there is still a lot more money to be made there, however I think Apple thinks it will continue to be a shrinking market as compared to iOS devices.
Can we really argue with the cash numbers?