You know what, I dont think it would be good for the Twins to fight, Dante should face a deadlier foe, who ever is the strongest in Hell or on Earth.
I mean they're brothers after all and they do care about each other. They worked together and defeated Arkham, Vergil told Dante to leave the Demon World as the Portal was closing, thats a sign that even though they dont like each other, they care about each other, just as Dante shedding tears for Vergil in the end of DMC3 and in DMC1, when Nelo saw the Amulet around Dante's neck, did he not feel something, to discover a memory which had been lost through his life as Nelo.
And okay, he did fight him again, but that was on the say so of Mundus and under his control.
Personally, I know they wont be the best of friends, but I dont want them to go up against each other again. Besides, Dante saw Nelo for the first time in DMC1, so Nelo wont appear in this that leads me to believe, since this is leading up to DMC1.
Im just rambling now