Yes, I'm almost certain too that due to the fact that they're releasing it as a separate game the old savegames won't work.
So, it doesn't matter anyway, I have already played around 30 hours (not as much as Velcas), and I have already felt in love. So I'm going to quit playing for now, and play again in August.
The game is so fun and has so much replayability that I'm sure is not going to be tedious to replay the 1st half of the 1st act again.
