Quin was an interesting character, but as time goes on his misguided search for the second Sith is getting a little dull. Since we all know who the second Sith really is, Vos' antics are taking a cool character and making him look like a total dupe. Dooku is playing him like a violin, and I'm pretty sure he'll either get it before ROTS or they'll keep him around to use as a character in the post-ROTJ comics. What his role would be there remains to be seen, but there is little doubt that Vader and Sidious would have him on the run pretty quick. In the meantime, he needs to pick a side once and for all.
I'm sort of hoping that Aayla survives ROTS, but based on what we've seen in the trailer, it appears unlikely.