No actually
Since DMC4 features two playable characters already, they should just try and make them as best as possible. Putting Vergil will only result to something pitiful like Special Edition, were Vergil is, well, no match for Dante considering the gameplay. He sure creates a slaughter easier than Dante, but still isn't as useful. And since no one uses "Katana-type" of swords, a costume is not an option either. Except if they give as Nelo Angelo again, but really it becomes kind of..."yeah, dmc9, did you unlock Nelo Angelo costume yet?

" which bugs me a bit.
Well time, will show^_^