Thing is, if the top is not beginning to precess (start to fall) and that his children aren't actually wearing slightly different clothing (though they are) or look slightly older (they do) and Cobb is still in the dream world that sort of makes the whole movie, and his character's journey pointless and makes the movie tragedy.
The whole point of the movie was that Cobb wanted to see his children again, that seeing them in the dream world wasn't good enough for him and that he had to let-go of his guilt over the death of his wife, Mal, to see them again.
If at the end he's still in the dream world (and that'd violate some of the rules of the "dream world" that he is since we see, or we're inferred, that he experiences the trip from the plane to home he just doesn't show up at home) then that kind of makes everything that happened in the movie and the development of his character pointless.
If he's still in the dreamworld then him getting to see his children is sad, seeing them in a dream wasn't good enough for him. Letting go of the guilt on the death Mal is pointless, as it doesn't get him to move on with his life.
So for the movie to make any kind of sense, for the character journey to be complete and true he has
to be in the real world at the end of the movie.
Or, as I often say, as much in the real world as we thought he always was in. (That's to say it's possible the whole movie
takes place in a dream world.)