Before I start, no-one is really 100% certain that this is actually Jamie xx. But, it does sound a hell of a lot like something that Jamie xx would create and produce. Bear that in mind when you're listening to it!
This track recently featured in his 'Day and Night Mix' (on the London Eye) as well as Pional's (a close associate) Fact Mix so it's a pretty good guess that this is Jamie xx's new material - and it sounds excellent.
Throw in some steel drums and you're all but sure it's him. There's literally nothing official about this track, but sources online claim that it's the first track of his new project (the one he's mentioned in his interview with the Japan Times).
It's a quality track. Hopefully it's his. The xx doing house-styled music. Love it.