He had to be dreaming at the end, and IMO this was given away an hour previous. When Cobb's wife commits suicide, she's across the street sitting on a different building and Leo's saying "come step back inside" like she's just supposed to fly over to him ... and he doesn't need to shout for her to hear him across the street, and any investigator would know she didn't jump from the trashed room across the street from her.
I think it was simply meant to be a representation of how he couldn't reach her, which is also why that room (from what we could see of it) was the same as the room Leo was in.
Having said that, at the end, the Caine Character is wearing the same clothes as in Paris which I took as a possible sign as Paris.
More generally, while I found this a well-made and complex film it simply didn't engage me on a emotional level and I left the cinema thinking "so what?".