There are three primary Marvel events to use the Secret Wars name: the one from 1984-1985, the sequel that followed soon after, and the one from 2015 which changed the Marvel universe as we know it, literally!
That said, should this storyline last across one Phase or several, having Battleworld be the endgame would make for a great conclusion.
Think about it, after Thanos has put the entire universe at risk, how do you raise the stakes from there?
That 2015 event is the one we specifically have our eye on for cinematic adaptation.