I'm 90% convinced that Jon is not dead, but I'm 50/50 on Aegon being the real baby Aegon. In the
Aegon's True Parentage thread, Eversummer put forth the theory that Aegon as we know him is not the son of Rhaegar but the son of Mad King Aerys and his daughter-in-law, Elia Martell. ADWD also gave us some reason to speculate that Lyanna was raped by Aerys and not by Rhaegar (as Robert suggested). If that is the case, then it could mean the three heads of the dragon (Dany, Jon and Aegon) are all children of Aerys, the Mad King.
Now
IF this theory proves true, then Aegon is who he says he is (and whom Varys claims he is), i.e. The Real Aegon™....yet at the same time, not who he thinks he is, i.e. the son of Rhaegar.
The reason I'm 50/50 on Aegon being TRA™ is because my first inclination after finishing ADWD the first time is that he seemed to be such a late-comer, too conveniently scripted to be the real deal. Then again, GRRM has established a great precedence for prominent figures being shuffled under a pseudonym, for either their own protection or for some one's personal gain.
Ramsay - Posing as Reek so that the real (original Reek) would be killed in his place
Jeyne Poole - Fake Arya
Sansa - Alayne
Tyrion - Hugor Hill / Yollo
BFS - Arsten Whitebeard
Arya - Her many aliases
Mance - Abel (not counting his time as Rattleshirt)
Elenya Westerling - Potentially posing as her older sister Jeyne
And more....
Some of these characters may live out the rest of their days (or at least decades) under their new identity. It is therefore not much of a stretch to think that Aegon could have been switched with any other baby at the last minute by Varys, then secreted away to live under the alias of Young Griff to protect his life, while waiting for the right time for his true identity to emerge (just as Littlefinger is doing with Sansa).
So all of that lends credence to the idea that Aegon is TRA™.
My 50% doubt comes from the fact that the one thing GRRM has taught me as a reader is that you should never take anything at face value. So ADWD presents us, at face value, the idea that Aegon is TRA™ and not an imposter. Therefore we may have to assume that he is not.