GRRM likes surprises, but I do not get the impression that he likes cheesy surprises. He wants events to flow from the characters and the logic of the plot, and he has worked hard to plant clues, prophecies, and false trails galore. This is why the story is so layered. He is now five books into a very complex, "dare you to figure it out" plot. If any of this has meaning, his options are being steadily reduced as he grinds to the end. Jon Snow and Dany kinda, sorta have to be in at the endgame unless GRRM is willing to tell fans, "Yeah, the first five books were all a red herring, and the real action has been offstage. You read 3,000 pages for nothing. Surprise, surprise."
It's late in the game to pull a new riddle-answering principal out of thin air. The options are dwindling (dying, mostly). Young Griff/Aegon seems to have been bypassed in the tv version. Since the tv and book versions are supposed to converge at the end, there would be some serious catchup to do if Young Griff/Aegon has a future. Bran, Rickon, Tyrion, Arya, Sansa, Jamie, and perhaps Benjen Stark (and just barely conceivably, Stannis) need to be sorted out, but they are all established characters. Aside from Howland Reed, it's getting hard to imagine a not-yet-introduced character changing the main story arc very much -- unless, again, GRRM is willing to play his readers for chumps and introduce a complete late-game wild card as the game changer.
Since “Aegon” isn’t in the show and won’t be (not this season and they gave Jon Connington’s stoneflesh to Mormont so probably never) I think he’s probably a fake who won’t have much relevance when all is said and done. I don’t know who’ll ride the 3rd dragon though if not him.
The show will start spoiling the books now, lol.
Being heavily spoiled didn’t dampen my enjoyment watching (or reading) though.