User blog comment:The Dragon Demands/Season 5 trailer officially released/@comment-1600847-20150130164618/@comment-5014364-20150131192825

I know, madness. But even the simultaneous renewal for both Seasons 5 and 6 was utterly unprecedented for HBO. That and we're hitting "the wall" of around season 6 where the core cast member contracts run out and they can no renegotiate for millions of dollars (JUST PAY THEM, it's money in the bank at this point!). As defined by pay scale, the "Level A" core cast members are the three Lannister children (Cersei, Jaime, Tyrion), Jon Snow, and Daenerys Targaryen.

As for whether baby Aegon 6 was ever mentioned by name in the TV series, I believe that Thoros of Myr mentioned him and his sister by name back in Season 3.