Personally I would wait. Having the development open for another two or three months would probably give enough time for some of the above mentioned features (and maybe some more) to get merged. It would also give time for more testing of the recently merged code. But I do agree with Werner, which is why, after the next two or three months of continued development, I would wait some more
"freeze" the master for a month or two and focus on testing, stability, bug fixes, translation and general release preparation. Instead of freezing the master it could also be possible to make the 0.15 branch and cherrypick bug fixes...
One thing to think about is also if it makes sense to support XP after 0.15 release (not just the XP itself, there is less and less applications that are supporting it). It is nice that we are giving extended support for its users, but we and its users have to realize that at one point, continuing using and supporting it is just like putting more oil on to the fire. If 0.15 should be the last version, then releasing it a bit later will give this users a bit longer support and a bit more features.
Just some thoughts, generally I love the progress that is being done and I am ok with what ever you decide to do