Attachment 23718
Oh look, it's Thor in Nova with Avengers characters.
(Admittedly both Cap and Tony are also Guardians of the Galaxy, Tony is in his Guardian's suit and Rocket is in the previous panel so it seems in retrospect that they are there in their capacity as GotG, though how Thor would know the GotG I don't know and if they are buddies enough to bring her along it would seem likely that they hang out on earth as well... as Avengers say?)
Attachment 23719
Oh look, it's Thor in All New X-Men with an Avenger.
Apart from at this point, you mean.
Attachment 23720
What this proves, more than anything, is the inconsistency of current Marvel continuity (hopefully Secret Wars will tidy things up somewhat), but it is pretty clear that two different writers, and three different editors, all consider Thor to be, if not an Avenger, then closely affiliated to the Avengers, and since the whole point of the Avengers machine seemed to be that pretty much everybody is on the bench, the distinction is negligible.