I can see some of them staying with Luffy at the end of the road.
Like Nami for example, they will most likely keep travelling and Luffy can't do it on his own. Chopper might tag along as their doctor.
I see Zoro wandering in the seas, a bit like Mihawk did, looking for a challenger.
Robin would be a good history teacher.
Usopp will return to his village to be with Kaya again.
Brook will be with Laboon.
Not sure about Franky, he can either stay with Luffy or go back to Water Seven.
Sanji will open his own restaurant, probably with Pudding for the dessert.
Jimbei will help the diplomacy between humans and fishmen
They will keep in touch though and see each other every once in a while