Personally, I hope for both a separate class, and a series of subclasses (including a psionic monk, paladin, and sorcerer subclass to go along with the GOO warlock).
I don't particularly want a separate Psion class, and I know I would never include it in any of my games that I run. I just don't care for it, and, as far as I'm concerned, the Sorcerer has absorbed everything unique about the 3e/4e psion except some spells (which can always be added in) and crystals (which are also easily added in as magic items / equipment). Not as familiar with 2e psion, but I'm still ambivalent about it. In my games, I would be more than happy to put in several subclasses that used psionic abilities.
Now, I feel that, first and foremost, one should design the Psion for its fans. So, there should be one just for that, even if I don't hold high hopes for it. However, I also want something for those of us who DON'T want it to be a separate class. A lot of people have a bad taste in their mouth from psions trying to be so different from everyone else - there's a lot of games that won't touch it if it tries to be so different. Yes, its different from arcane and divine magic. But I don't think we have "divine" and "arcane" classes anymore - we have the cleric and wizard, and then a bunch of others who are different from both.
So, I feel we should have our cake and eat it to. Or, more plainly, we should have two sets of Psions. One is a full class that want that, and it feature predominantly in games that want to make an issue of it. And then a set of subclasses for those that don't want to include an entire different class into the game for those who want to dabble in psionics without it being a huge deal in their game, or who feel its too sci-fi to be in a fantasy setting, etc.