Some bungie folks have let some things slip already. D2 will be a "start over" or in other words a new game altogether, D1 players will get a special thanks (level 20 on day 1 for example), so no rolling over characters (a D1 server will continue for those wanting to keep playing that), D2 focuses on Cabal & Saturn (it will be larger than all existing maps combined)... That's a summary of several leaks out there.