I am a bit surprised to hear that there won't be a 2007 Hi-Def re-release. I expect that's due to the fact that the movies have been released on DVD - and that's that. If a HD set is to happen, looks like Lucas will wait for the next-generation of discs - whether that be Blu-Ray or HD-DVD. Surely, then we will see a re-re-re-re-re-re-release - and it will no doubt include further changes, high definition, more special features, etc, etc. By this point we should also see some modifications to the prequels and perhaps even TPM's puppet yoda replaced with the digital model from episode II. That's not wishful thinking, as there was a "warm up" for episode III which involved replacing puppet yoda.
Also; Greencapt - I completely agree with your theory! Home theater (as long as the screen is fairly big, and the sound system's good) is the best way to go!