i always thought it'd be cool if palpatine were to give anakin a brief history of the sith - like mentioning the sith wars, especially because there's no explicit reference to it in any of the movies. the closest they get is in ep 1 when one of the jedis says "impossible, the sith have been extinct for a millenia." i'm willing to bet that something like this could happen, just because most casual viewers of ep3 won't know what the sith are getting revenge for.
ps - it'd be cool for palpatine to take anakin to a sith temple, if one exists.
"It will never be overtly revealed. One of Lucas' few good traits is that he leaves some things as a mystery. Everyone can have their personal opinion if things are left untouched."
I disagree. It isn't a 'good trait', its just bad writing and planning. I think Palpatines story will be told in a novel or comic book after Ep 3 is out. The only thing Lucas told EU creators to stay away from was the Clone Wars, since he was planning on telling that story. After Ep 3, if Lucas really plans to drop SW forever, the EU will be open to any story that someone wants to tell. I can't wait, since I think the EU stuff is 10 times better than anything Lucas himself has done.
There is nothing a all lazy about not explaining in detail every single part of what anyone would ever want to know. It really is not greatly relevant to the storyline who taught Palpy; it is only of curious interest and hence is not a big gap if it is not there.
Whatever the EU says will be someone else's interpretation of the case; the only relevant issue when talking of the storyline of the films is what GL's interpretation is.