While I see where MS could be going with this, I firmly believe that they would not completely leave their customers out in the cold on this one. They have already told us that the games will not move to anything other than DVDs, and I highly doubt that developers would start making games on hd-dvds if there were such a small numbers of existing consoles on which the games would play. The games still fit perfectly well in ~ 8 GB and with improving compression algorithms, they can use that space more and more effectively. Plus, they can use more than one disc, we have the technology. I don't understand why people don't use more than one disc anymore. It worked fine in the PSX days, hell it even worked fine for the Cube and RE4. It's not like back in the day when we had to switch sides of disks between each level. We're talking about a switch once or twice in a 20+ hour game, who cares? Have we really gotten that lazy?
Honestly, the only thing I'd want out of the revision would be that bigger HDD. I don't give a crap about the HDMI, 1080i is fine for me, I can live quite easily with a white system and I can live without an HD-DVD player. I'm still running the thing on a little 14" JVC tv that outputs a great component signal and probably will be for the next year and a half until I move out.
For my purposes right now, my 360 does the job just fine and I don't regret the purchase one bit. All depends on your taste.