When GL makes the Ultimate editions, its likely he will replace the emperor in ESB with Ian McDiarmid. I think this is a great idea, for continuity and because IM has really brought to life the character of Palpatine. It would be silly not to change this (and easy to do as well).
However, there is another actor (CLive revill) who has been in ESB for over 25 years. SO is it right to suddenly cut him out of the movie after all this time?
For that matter what if they replaced Anakin as he's dying or when he is a ghost with Hayden christiensen? The actor who played old anakin (Sebestain shaw) passed away years ago, wouldn;t that be sort of pissing on his grave?
Or replacing puppet Yoda in ESB and ROTJ with digital Yoda.
All these changes make sense when thinking of the saga as one big six part epic, but they also are insulting to the people who did fine work in the first place and for almost 30 years have been able to say they were part of the SW phenomenon.
BUT:
If you continue to make the original versions available, then none of this is an issue. They could replace every scene of OBI-wan in the oT with Ewan McGregor in aging make-up if they wanted to, and it would be no insult to Alec Guiness' memory, because his original contribution would still be perserved.
And the same is true for all those FX artist who worked for years to create those FX. Nobody is saying their can't be an upgrade, but just keep the originals around as well as a record of what done back in 1977.
Do you follow?