Alex public memcached development at Facebook seems to stopped for the last ~2 years. Is it really the case or still improving but not making it public? Also can we expect management tools for memcached in the future from Facebook?

Facebook's version of memcached has diverged significantly from the public version, to the point where pushing it upstream is at the very least unproductive and likely disruptive. It is our intention to eventually open source the entire stack, but as it's still very much in active development it's relatively low priority at the moment (note that this is the conservative viewpoint, people with significantly more seniority than myself want to see it released sooner rather than later, and no one above them disagrees).