Hmm, well assuming this is real, i'll be very sad if they replace Rueben. For one he seems to have a passion for the role and even if he's not always been the voice of dante, I think he's made it his own now, I don't think they'd replace him...but then again I never thought kojima would have the disrespect to throw away David Hayter without so much as a thank you, so who knows.
Nero could be recast but his current va(Forgot the name) does a great job as is, and a more grown up nero would make dante much older, unless they are going with the whole late 50's dante which could admittedly be interesting, thoguh I think any game afterwards would have to go back quite a bit.
There's the possibility as well of a new main character but I don't think capcom should do that, we saw how it ended with nero and we damn well saw how it ended with the the reboot, nor is it the time for a sparda spin off as cool as it'd be.
I think they feel they've wrote themselves into a corner with dante given how powerful he is now, afterall he did kill the god of hell in his first entry, everything else is a step down xD, but I think there could be ways out, one idea i'd love for them to elaborate on in dmc is the artificial demons idea which was very badly used for the most part in dmc4, or the possibility of a new leader of hell could be a simple but possibly effective way of making things a challenge for him again.
I'm all for experimentation but DMC5 needs to play it mostly safe I think, hell go back to a younger dante if need be, there's like 10-15 years of his life we have'nt seen between 1 and 4 i'm sure there's storytelling possibility there somewhere.