If we're digging this thread up. I would like to proclaim that I know the ending with 99.9% certainty. Yes the moral is that it doesn't matter because Dom accepts that reality as THE reality, but there is still a correct answer. The answer goes back to their explanation of the totems. The whole point of the totems is that you have your own and you know it's weight or it's properties so that if you are in someone else's dream those properties will change and you can tell it is behaving abnormally. It means nothing if you are in your own dream. The spinner is Mal's and so while Cobb doesn't know the properties of the spinner, but he's in his own dream so he thinks it does. The spinner wobbles as it is losing momentum so it will fall, however he is still dreaming and the whole heist is either inception on an outsiders' part or his own mind trying to bring his journey to a conclusion in the hopes of waking him up. Remember his own worlds about the mind wanting catharsis, for Dom that would be returning home to his kids. Sounds like a dream ending to me...
Personally, I think it's an outside party, because of some of the statements addressed to him, such as "Come back to reality Dom." There are several other suggestive lines throughout the movie, but they're always particular characters. But I feel like this part is speculation.
The point is, the top will fall, but he's still dreaming. After a decade later, you're welcome.
