I thought that made complete sense -- he'd traveled with Amy and Rory and, as he's done with all previous companions, they had departed to get on their lives, much as Martha or Sarah Jane had left the TARDIS in years gone by. In this case, though, we don't know the reasons why Amy and Rory left the TARDIS. The younger Doctor's reaction to them in "The Impossible Astronaut" seems to suggest that the Doctor wasn't expecting them to travel with him again any time soon, but then circumstances forced him to change his mind.I wondered whether everyone on the beach is a clone except the Doctor. Just to be different. The whole "dropped them off to get on with their lives" bit didn't make any sense to me.