I think Rockstar have a problem here. They will definitely want to bring missions with the planning and prep work back again, but if it's just heists and robberies it will feel recycled.
Personally, what I think they should have done with V was have no antagonist and crafted a story of the corruption of the high life, maybe have the three heroes strike it rich then start being the a**holes and creating the tension that way. This game didn't really need an antagonist, and at times we struggled to see who it really was until option C was like "oh kill these people and you're good." Having no actual goal for the plot would have been a brave move but Dan Houser's writing would have totally justified it. Just make a game purely about robbing people and ego tripping as a result.
Anyway, do you want heists back in GTA VI?