Judging by history, I'll go out on a limb and say....
Skal - Lottery
Briscoe - First Round
Lee - Late First Round/Early Second
Poythress - Second/Early Second
Diallo (if he signs) - Lottery
Murray (if he signs) - First round
Totally misread the question ... I think they're are 18-20 guys in the league right now so maybe 25 or so...
We currently have 18 guys in the league. Mohammed is done after this season. Prince probably has a year left if he wants it. Of the 7 declaring, at least 5 will be drafted.
A safe bet for UK players on NBA rosters next season would be 22 or 23.