While we can't be 100% sure it's Jamie xx, this tune has appeared in his recent Night + Day Mix, in his show on the London Eye, and in close associate Pional's Fact Mix, so we can make a fairly good guess that it's him.
Add in the steel drums about halfway through, and you've as good as got yourself a guarantee. Although no official information about the track has been released, given the fact it's starting to pop up everywhere, we'd have to assume it's Jamie's next solo release, possibly off the forthcoming project he mentioned to the Japan Times.
Beyond that, there's little more to say. It's an absolutely gorgeous tune, and actually sounds quite a lot like The xx doing house music, as opposed to some of the slightly more experimental work Jamie has put out under his own name. All we can do now is look forward to a release (and hope that Four Tet collaboration mentioned turns out to be true!)