I think Dante will be the lead in DMC5, with Vergil/Sparda the other protagonists, and Nero's probably only be a minor sidekick. DMC5 gotta use Nero to a certain extend: by telling us who the hell he is, Capcom should be able to tie every Sparda-related personnel together.
Personally I don't mind seeing Nero again, just not the lead PLEASE - wanting to see him using DB on bosses is okay, but using him for more than half of the missions is not. If there'll be a bloody palace and I can use him there, that's good enough.
Dante gotta be rich in DMC 4 - who can afford to get a new door every time he sends it flying away!? and look at the antiques he got - those are some high-maintenance stuff