Some will likely stay together, some will do their own thing, but they'll always be down to reunite whenever.
I see Nami and probably Zoro staying with Luffy at bare minimum, since the latter's biggest fear is being alone, he'll want to keep going on adventures, he can't do it without a navigator and Nami's dream to map the world will take a very long time. Zoro would stay as Luffy's right-hand and fight potential challengers for his status/title as the greatest swordsman while sailing, although there is a small chance he could also settle and open a dojo or something.
Usopp will likely go back to Kaya, I imagine Sanji would want to stick around the All Blue, Brook will want to be with Laboon etc.