You really think he won't offer the originals later in the hopes of selling them to people who bought the SE's?
Seriously? You think Lucas isn't greedy? The guy who put Ewoks in RotJ because he wanted to sell teddy bears?
Then why didn't he do it with DVDs if he was so greedy? Why not pull a LOTR and release the OT on DVD, wait a year or so, and release the SEs? You don't think that'd make more money than what he did?
No.
LOTR SE's was about a director adding cut material largely consistent with the oriignal [and the book on which the original was based], not changing plot points,
SW SE's about a producer/director tinkering with his own work and generally leaving fans displeased in the process.
If Lucas released the "real" versions first, most people would get the originals and bother with the screwed up special editions.
Therefore, Lucas needs to sell the special editions first to maximize his profit. And, in fact, that's what he did with the DVDs in 2004. He released the special editions
first and the original versions two years later.
It's all about greed the way he's doing it.