I'm prediction that at PAX we'll have a playable PVP arena, with guardians locked at the level cap. We'll be able to choose from all 3 classes, with a separate characters for each different focus. We'll choose from two or three different arenas to battle with a handful of other players.

My guess is that we'll be seeing PVP at PAX as opposed to co-op or single player missions/strikes just because of the logistics of recycling and reusing leveled characters for four days. Level-capped guardians seems like the easiest way to do it, and PVP would probably be easier to implement as a standalone for their booth/kiosk/corner.