The only vault hunters from BL2 appearing in the trailer are Maya and Zer0. Axton, Salvador and Krieg are also nowhere to be found, so Gaige isn’t the only one apparently being left out. My guess is some of them will maybe make surprise appearances Gearbox doesn’t wanna spoil too soon. If not, they’ll probably show up on DLC or at least get a mention of some kind.
Also missing from the trailer: Mr. Torgue, Dr. Zed, Athena, Janey Springs and Fiona.
Personally, I really wouldn’t mind even if they don’t appear at all. I don’t think it’s necessary for every single still living character to make an appearance in this game, no matter if they’re a favorite of mine or not. Specially if it makes the story more convoluted than it has to be and they feel shoehorned in. I hope that if we get any cameos and appearances from them that there’s more of a narrative reason for the inclusion than just fan service. No single character is more important than the story and no specific previous vault hunter is more important than any of the others in any way.