My hopes:
Well, since Joey is going to be a spin-off, I'll leave him out.
For the rest of the crew:
I hope Central Perk burns to the ground, while tragically Ross is trapped inside. I'm not sure if I'd prefer if he's burned to death in the fire, or just horribly disfigured for the rest of his life - but either one would satisfy.
Phoebe and Rachel run off together and join a man-hating feminist group and spend every day watching The Vagina Monologues and protesting whatever the flavor of the month protest is.
Chandler and Monica move to Long Island. They have lots of kids. Monica has one infidelity with a weird guy who looks uncannily like David Arquette, and Chandler has one infidelity with Janice who is tragically run over by a bus on her way home after the zesty session. Neither Chandler nor Monica ever find out about the other's indiscretion, and live basically happily ever after.
Either that, or Monica wakes up to find out that she's still fat, and the entire series was just a dream.