He missed the cascading kicks. Therefore, even waking up out of limbo wouldn't take him directly back to the real world. I vote he's still dreaming at the end.
Me too, he's still in limbo, but he created his own version or something.
But you could just go "It's all real, the top stops spinning 1 second after the screen turns black'", or that the whole movie was a dream and that his todum doesn't work because it's his wife's and he's still in a dream for many years.
It's a fine movie, but I didn't find it smart, it just wasn't as stupid as most movies are.