I really do like the ongoing idea of the first sequel being subtitled, "To Boldly Go", followed by either WNMHGB or WNOHGB. I think it rocks. But I would imagine the idea has been spun around countless times, and if they truly have yet to arrive at anything definitive, they've determined there is an issue with this concept.
This works best for me. Star Trek in a smaller font, or appearing first and then drifting off into the distance... with TO BOLDLY GO zooming into view afterwards.
Same deal with whatever a third is called. Think of titles, phrases, that could standalone and scream Star Trek - even though most won't give up putting that and a colon before it all the same.
It just screams "Do it!" to me. Although they'll probably end up going for something Star Wars pulp fictiony... like an Attack of the, or a Vengeance from, followed by [insert well-known alien race here].