Pcerceui said he wants to merge most of his changes in Linux 4.11/4.12 so we should probably get a minor firmware update at the end of this year. (if not before)
It's already too late for 4.11, so it will (hopefully) end up in 4.12.
The main problem that slows things down, is that we can't submit all the patches in parallel, most of them depend on others being merged first. Also, submitting patches can take a lot of time if upstream developers require us to make non-trivial changes to the code, which is the case right now.
We don't need everything to be upstream to make a new firmware release, though, we'll make a release when all the bugs we know about are fixed. But we're dedicating more time to upstreaming right now.