I... I think it's rather a good theory, actually; I'm really quite excited about it.
-Thing the first. Moffat is on record as saying, regarding "The Impossible Astronaut", yes, that really is the Doctor, and yes, he really did die.
-Thing the second. In this most recent episode, "The Almost People", a great deal of time and effort is put into convincing both the characters and the audience that Flesh!Doctor is the Doctor in every way that counts.
-Thing the third. Right at the end there, we have this:
[DOCTOR] Your molecular memory can survive this, you know, it may not be the end.
[FLESH!DOCTOR] There may be a way back from this.
-Thing the fourth. Back on the TARDIS, we have this:
[DOCTOR] The energy from the TARDIS will stabilize the Gangers for good; they're... people, now.
WHICH BRINGS US TO MY THEORIES. Flesh!Doctor will be back, somehow. THEORY THE FIRST, which I've seen other people play around with: Flesh!Doctor is actually the one that gets killed by the Astronaut. THEORY THE SECOND, which I've not seen elsewhere, and which I like a hell of a lot better: original!Doctor will really actually truly honest-to-god die. Flesh!Doctor will replace him, and the energy from the TARDIS will stabilize him for good and he will become Time Lord people.
...WHAT SAY YOU, INTERNET?
In other news, the Doctor knows about his own death now, hahahahahahaha oops? :D