1.) Yes, the SE discs will make a ton of money. There is no doubt. Just look at the Amazon.com chart listings for best selling DVD's.
2.) Again, releasing both versions (in my mind) would make the most sense. Fans of the original could get them. Fans of the SE could get what they want. Fans could also buy both. This would give the truest perspective of what has changed. It would outline what Lucas had to work with in 1977,1980, and 1983; compared with what was done in 1997 (and perhaps what would be done with 2004 technology, assuming any more changes were made).
3.) Releasing the original versions would be a nice nod to all the old fans who grew up on Star Wars and made Lucas(and its cast) wealthy.
4.) From Lucas's stand point, it would make him even more money. Not that he needs it, but perhaps some of it could be donated to charity.