while small and i mean small before fighting Berial as Nero there's a sign that says "Mundas lives" in latin i think which could mean Mundas is gaining more strength and so it connects to DMC 2's ending with dante going straight to hellSince we haven't turn around public perception for Nero i suggest putting him on the back burner for a while. The main problem people had with DMC4 story-wise was that it answered no question(from other games or this one) so it didn't feel necessary.
So i think doing a dmc5 tieing up loose ends would be best as well as giving Dante renewed purpose by advancing the core plot. Nero is more of a supporting role but he is still playable and you will get answers about him.