I confused my Targaryens! What do you think of this? It seems like a necessity due to the time/budget constraints of the TV series.
Overall, the TV series has been pretty true to the books. Yes, lots of characters and scenes have been cut, but I think we are now going to start seeing straight-up changes to the materials.
IMO either they cut him altogether, or a very simplified version will be introduced at the end of season 5 only (they would reveal his existence only as he lands with mercenaries, not before).
But all and all, I tend to think they will streamline things and in effect they will merge Aegon and Dany. I think in the show the Prince of Dorne will make an alliance with Dany, securing her eventual landing in s6. They will cut the older son who gets fried in the books, and at the end of the season instead the Prince will reveal to the Sand Snakes that he never truly intended to marry Myrcella and Tristan, that he pretended, to buy time and to get a Lannisters hostage, and he plotted with Varys to offer Tristan's hand and an alliance to Daenerys.
They'll stick to the basics, which is that Dorne is aligning itself with the Targaryens.