I've got a theory,
SO. My thought.
Cobb is definitely in a dream. His wife isn't there anymore- whether she's deceased or not is an academic question. If Cobb's in a dream, the question of the top falling over or not just after the camera cuts away becomes irrelevant-- because the only way we know that the top will fall over in reality is because one character in a dream mentions it to another.
The various members of the inception team, I have two thoughts. Either A: they're all aspects of Cobb's psyche (Joseph Gordon-Levitt as superego- which is why he and the awfully id-like Tom Hardy clash so... Ariadne as anima)- possibly excepting Saito, who would be the dreamthief who's coming to extract Cobb.
Or B: they're a team who've found their way down deep enough to snag Cobb's attention.
One thing that makes me think it's a dream, as well- notice how the closest Cobb comes to being harmed at any point is being washed up on a beach? Everybody else on the team gets the crap kicked out of them, and at least one dies (maybe two, if the Cillian Murphy character is a part of this extraction team). But Cobb? Completely unharmed, completely ignored by the projections in all 3 levels, despite his apparent intrusion.
It was an interesting film- I hope to stop mulling it around at some point in the near future.