Not really, because I
couldn't care less (so you don't get at me for putting "could" lol) either way. I'm unbiased. I'm open to either possibility. Either explanation if proven definitive would be acceptable to me.
But as far as assumptions, IMO if you believe the ending is a dream that's 1 assumption you have to make. It's a dream. Period. It explains everything.
On the flip side, if you believe it's real THEN you have to make a whole list of assumptions and theories and that's what makes it hard to buy. At least for me.
And just to clarify: If anyone reads Maglor's post (recommended) he talks about the two types of dreams in the movie. 1 as "Natural" and 1 as "Somnacin". To make it more simplified, let's call 1 "Natural" which is what we all have when we sleep and let's call the other "Machine" which covers ANY type of dream that involves using that machine (in the suitcase) in the film.
There's actually a third type of dream that Maglor doesn't mention, and this is the type of dream I believe the ending is. I call it "Comatose" dreaming. Which is initially a Somnacin/Machine dream followed by Comatose/Natural dreaming as result of a severe conscious/sub-conscious complete mental breakdown. This also carries over to the real world where the person is essentially considered comatose/a vegetable.
This type of dream/outcome IS mentioned after the team is attacked by Fisher Jr.s sub-conscious guards on the first level down of Inception. They mention how going into Limbo combined with the powerful sedative being used could cause someone to go comatose in the real world and end up with a brain like "scrambled eggs".
Think about this: Fisher Jr & Saito supposedly go to Limbo after they're killed on the 3rd level down. But Cobb and Ariadne apparently get there by inducing a 4th Somnacin/Machine dream (still not sure how that's even possible and how simply going down another level will immediately put them in limbo!?). And if the level Cobb and Ariadne go to is truly limbo, how was Cobb's projection of Mal already there holding Fisher Jr hostage!?
Not to mention if that level is truly limbo, that means that Fisher was actually in limbo LONGER than Saito. And it also means Cobb was in limbo ALMOST as long as Saito as well. Because Fisher Jr dies BEFORE Saito. And Cobb supposedly goes to limbo shortly after Saito dies.
Yet Saito is an old man and Fisher Jr./Cobb aren't!?
I think all the dreams within dreams within dreams within dreams plus extensive time in limbo on numerous occasions finally took their toll on Cobb. And at the end when he's finally with his kids and happy and everything is picture perfect, in the real world Cobb is a complete vegetable on the plane in a permanent comatose.