If you buy PT2 now (ie so close to PT3's release), they'll give you a significant discount on PT3. Same with PAHUD. So if you don't want to wait until PT3's release then by all means buy the current version.
They say PT3's due out in the middle of March, but they also originally said that it would be out in Jan/Feb - they're constantly pushing the date back trying to perfect the program, so if you want to play any time soon with PT, buy the current version.