Nightstorm, you might want to think about the idea of storing 2 sets of content for the 2 TVs. For example, if you have a lot of HD content, and you "max it out" for the 720p TV in your bedroom, that content won't look as good on that future living room set, capable of higher resolution. Upscaling from a lower resolution master can't create as good of a picture. On the other hand, if you render your content for the future (living room 1080p) set, downscaling those videos to 720p from a higher/highest quality render is generally no problem (looks fantastic on both sets).
Of course, relative to the current

TV hardware, this is all for nothing, as it can't handle full bandwith 720p or 1080i/p (though 720p output can look better than DVD even compressed as it is for the current

TV limitations). But, should Apple finally roll out 1080p-capable

TV (or should you use a Mac Mini or many other current hardware options capable of outputting 1080p), you may find it simpler to simply render your video for max resolution and then downscale to lesser resolution devices.
Downscaling from a great source yields a fantastic picture at any lower resolution. However upscaling from a lower-resolution source yields a less-than-optimal picture at higher resolution. More simply, if you scale down a big jpg, it will still look great as the picture size shrinks. But if you scale up a small jpp to a bigger size, the jaggies appear. Same basic concept applies (though it is better disguised in moving pictures).