In all the discussions regarding the cliffhanger, people always assumed that Ross would be the next one to come into Rachel's room to find Joey "proposing" - when all we know is that Ross left an elevator with some flowers in his hands, and we don't even know how far it is from the elevator to Rachel's room.
What if either Monica, Chandler or Phoebe were the next to come into Rachel's room? Or, currently my favourite idea: Jack & Judy. I'm pretty sure they will be in 901, since Judy told Ross she would be back with Jack later, she just came around to give Ross the engagement ring. I'd really like to see a typical "Jack-ism", where he sees the ring, turns to Judy and says: "That ring looks an awful lot like your grandmother's" (although the chance of that happening are rather slim, if J&J are the first to enter, it's most likely going to be Judy freaking out)
Andr�