Look at it this way- every weapon in the series has a clear origin (perhaps aside from the swords in DMC 2). Yamato in DMC 1 was just a reskin of Alastor, but even it had an origin story.
Assuming Vergil's probably not getting much new story or fighting any new bosses, where would this 'new weapon' come from? You can't just pull an awesome weapon out of nowhere, and people would likely complain more if his traditional weapons didn't make a return. So yeah, I don't think we need him to have new weapons when they're already varying the movesets available to his existing devil arms.