I really hope Belmont 3 is Christopher. Richter's cool and all but he's been in, what, five games already? (I suppose you can argue against Simon this way, but c'mon, he's the original.)
Though Sonia or another original Belmont would be neato as well.
Sypha would also be cool, and it'd further drive home A) Dracula's Curse influence, and B) having more than just whips and one sword guy to work with. Trevor does admonish her not to try to find him... I imagine there's not much left for her to do than completely ignore his directions and follow him. (Anyone noticed that he tells her to go to the forest? Where a Cyclops might decide to stick her in a statue? lol)
I guess the one problem with the last scenario is that Grant would once again be thrown under the bus. Poor Grant. Nobody likes him.