Battle Arena decks are legal, but the gimmick with them is that the cards they contain are from their original sets, and don't get a new set symbol. This didn't make any difference for the first 1.5 (the Xerneas/Yveltal one, and the Red Genesect Collection), but for the Mewtwo/Darkrai one, and this one, the main purpose of them is to reprint Expanded-legal cards without bringing them back to Standard. So they won't be STANDARD legal, but will be Expanded legal, and obviously some cards (like Sycamore/VS Seeker) will be legal in Standard.
Hmm... I don't know how I feel about these picks. Keldeo makes sense. Guess we're never getting a Shaymin reprint, though, lol. (Who knows, maybe they'll break from the 2 EX's per deck trend. I could actually see them putting, say, a Seismitoad in the Keldeo one and a Shaymin in the Rayquaza one.) I'm probably going to skip these like I did with the Mewtwo/Darkrai ones, though, seeing as I have zero interest in Expanded. (Plus I already own Keldeos even if I did care.) The only thing that might convince me is a large number of VS Seeker. (Or Shaymin.)