What really happened at the end?

I find 12B to be intriguing but let’s leave this at 2 options for now. It’s either real or it’s a dream.

I find it interesting that nobody has mentioned some key facts here such as: DiCaprio throughout the movie is constantly being driven by the same haunted image of his kids. He is filled with regret that he doesn’t see their faces that “last time”. Also throughout we see his kids showing up in his missions during the dreams, basically distracting him. Translation – He doesn’t care whether the totem stops spinning or not because he doesn’t want to miss his kids faces.
Next fact – When in a dream, the subconscious has a way of letting you know or warning you that you are in fact in a dream. One of these ways is that people unrelated to your dream, in essence the extras of the dream, will start to look at you or whatever is out of place. This in essence, let’s you know that you are in dreamworld. Well, what I instantly noticed is that this begins to happen as he walks through the airport, I believe after he passes customs. Everyone starts to look at him, and it seemed to me that he noticed for a split second but disregarded it or something changed which caused the people to stop looking. Maybe I just imagined this.
Then there is also the fact that the events of this movie, as it seemed to me, all occur very quickly. 50 years of limbo occur throughout a ten hour plane ride. So it seems inconceivable to me that Michael Caine would be in Paris or wherever the hell they were, and then suddenly be in the USA to pick him up. So Caine being there to me is an instant clue that this in fact is a dream. Plus Caine seemed to be his pops, not the wife’s. After all, she was presumed murdered. If Caine were the wife’s father, I doubt he would still be on speaking terms with his wife’s murderer.
So we get to the final scene. Thing is spinning, and it looks like it could keep going on spinning, thus signifying he is still dreaming, but it also looks like it is beginning to get a little wobbly, and it may in fact stop but he is too distracted by his children to care or notice. Either way, we don’t truly get to find out because it jumps to the credits, thus letting us come up with our own conclusions. But though it may look like it could stop, the fact is it doesn’t.
This to me all adds up to: He is dreaming. He has now entered his own personal limbo, where he has finally found peace. Just my humble opinion, but what I can say for sure is, Great fucken movie.

This is just a movie, written with an ending that makes no sense so that people can’t figure it out and keep talking about it.

Nothing more to it than that. There is no 12a, 12c, this or that theory, it`s just movie deliberately written to be ambiguous so that you keep thinking and talking about it.