Thanks to the WGA script that was released to writers for awards nominations and the junior novelization of Star Wars: The Force Awakens, we now have confirmation of major plot points involving Luke Skywalker, and that cliffhanger (almost literally) of an ending.
The film, of course, ends with Rey seeking out Luke for his help, presumably for his training, flying with Chewbacca and R2-D2 to a mysterious planet. That planet now has a name: Ahch-To. The name is revealed in the script and the junior novelization, and was confirmed by Lucasfilm's Story Group member Pablo Hidalgo on twitter.
So if you can see the WGA script, yes, the name of the planet from the end of the movie is there.— Pablo Hidalgo (@pablohidalgo) January 1, 2016
The novelization also reveals another major piece of the puzzle: yes, this is where the First Jedi Temple is located; Luke Skywalker found it, then, which begs the question, did he also find what he was looking for there, and why did he never come back after finding it?
Never-the-less, those ruins are that of the first Temple, on the planet Ahch-To. Where it goes from there is anyone's guess, but it's a safe bet we'll find out more in Episode VIII in less than eighteen months (and probably in a novel or comic or two before then). Oh, and for the record, it's the ruins of a real-life monastery in Skellig Michael, Ireland used as the on-location set.