KFC and Phee make a good point. The only thing left to explore with Regina is endgame, which means this new romantic interest either has to be someone who is already full time (Hook) or someone they plan on making fulltime or at least someone who is ok with being a guest star or “also starring” every episode (RH). Like Phee said, this relationship won’t start off easy; Regina has a lot of baggage and a lot to make up for before she can really be open to a romance. This is one of the reasons I really liked her and Hook together (except I’ve now jumped ship and am clinging rather desperately to Hookriel).
I guess it could be someone new except adding another new character on top of PP, Tink, Ariel, random Lost Boys and maybe Ursula and Triton feels heavy and unfocused and too many new characters was the problem last season. It almost has to be someone we already know.