Clearly the ending is MEANT to be ambiguous. Anyone who argues that it's NOT meant to offer at least 2 possible interpretations is being disingenuous.
I'm of a mind that there's only one really correct interpretation, that the ending is a dream, and I do really hang this on the children.
Consider how the children are portrayed throughout the film: Always golden haired, always dreamlike, always crouching over, about to turn round. That is the image that is burned into his subconscious (T'Baio
: damn I love that word alright?); and that is the image we see when he sees his children - indeed, it unfolds exactly as he wanted; the children who always ran away instead turn to greet him.
But time passes. Kids get older. Kids wear different clothes. Kids might be doing different things. Maybe you see one of them hanging around the house but the other one is at a friend's house. The sheer perfection and relation of this moment to the dream image - added with the fact after Cobb wakes up we see everything from his viewpoint, in, additionally, a rather glossed over fashion - make it unambiguous to me that the ending is a dream. Sure, maybe it could just be a bleeding huge coincidence, but candidly I think the moment is signalling the audience. We've been impressed with this one specific image numerous times throughout the movie; this is the payoff.
This isn't quite like, say, Total Recall
, where I say the movie is a dream simply because that's the more interesting answer (not necessarily the answer that makes more sense); I really think it's hard to see the film's conclusion as anything other than a dream.
Is it possible to interpret it otherwise? Well yeah, but everything is, isn't it? I still like my idea that Ariadne is really Mol as a young woman but I don't have any concepts that fit it into a framework that makes sense (when watching the film I also toyed with the idea that maybe only Mol was real and she'd entered Cobb's mind to try and wake him
up, but that also doesn't make sense...)
I dunno, I think Inception
is less of a Rorschach test as far as dream meanings go and more of an open-and-shut puzzle scenario... but then again.