Not even going to pretend I know what all would be involved to make that happen, but I know that SEGA has ported Phantasy Star Online 2 to the Vita, and beautifully so I might add! Perhaps Spiral Knights could also make the transition? I can't speak on behalf of anyone else, but I *LOVE* the idea of playing this game on Vita!!!
But Three Rings is the holder of Spiral Knights and is, for the most part, the main developer of it, not SEGA.
Three Rings design team ≠ SEGA design team.