I can't say I agree about Destiny's mission, I can't think of any mystery more interesting, certainly not within Stargate mythology anyway. As for seeing them get home, I'd be very surprised if that was ever the plan. It doesn't even seem like something worth seeing to me. I'd rather see them solve the mystery and be left stranded than see them randomly find a way home.
I'm guessing they had written themselves into a corner with the mission. What could they possibly dream up that would be satisfying. It's not like they would reveal the true meaning of life, the real face of good, or anything like that. It would just be some fictional mumbo jumbo that couldn't possibly live up to expectations.
Mr Awe
There is no way they could've come up with a satisfactory conclusion for this "mission." It's all about the journey, anyway. Really, what could they have done with it? Some beings ascended before our universe came into existence and helped create and shape it? We've already got the Ancients who seeded human life throughout the galaxies (or something), so it's not like the existence of some pre-pre-Ancient super race would be any kind of shocking revelation.
It strikes me as something the
Destiny crew might make baby steps toward solving over the course of the series, and at the very end they might get some big clue, but never a full-on reveal. It's the sort of thing that just wouldn't be satisfying if you put all your cards on the table.