Out of the most discussed possible new Titan figures, I think Trypticon is the most likely. These days they tend to tie in with whoever is the most popular in the comics and games with the Generations toyline.
In recent Trypticon was in Monstrosity and depicted as titan size. He appeared in the last 3 console games (admittedly deactivated/transformerd in the last two), also titan size. He also just got a Kre-O figure (opposite of titan size I guess

). I think if he was to put in another showing in the IDW'verse, maybe in the sequel to Monstrosity or in the universes current era, it may just push the scales enough for Hasbro to make a figure of him.