Probably it is a bit soon to ask that question, considering 1.7.0 has been recently released. Also note that it is likely that 1.7.x minor versions will be released before 1.8.0. Anyway, I remember this post in which the high level scope was mentioned for 1.8/1.9: http://www.question2answer.org/qa/33047 . Maybe Scott will have to revalidate that roadmap.
What I can (almost) confirm is that one additional feature will be added to 1.8 which I've been working on. It was motivated by this post: http://www.question2answer.org/qa/41792. It should be almost finished and I'm currently waiting for Scott's review. Anyway, anyone can test my patch-48 branch and give me feedback. The more eyes involved in developing the product the better quality it'll have :)