I feel like I couple things are being overlooked by a few of you...
This will not make Exp. Share obselete.
You need multiple energy down on your active for this to even be "better" than Exp. Share
and even then, only setting up one Pokemon is a lot riskier than spreading your energy.
Which leads me to my next point:
This card is a lot easier to play around than Exp. Share.
Lysandre, Escape Rope, etc.
Having your active switched on you is not an uncommon thing in this game.
Wish Baton does nothing, unless that Pokemon is knocked out.
Exp. Share works from any of your Pokemon being knocked out, as long as it's active.
On top of this... it means your basic attackers won't be able to use Fury Belt, as this card will be attached to the
Pokemon you're setting up, as opposed to Exp. Share which is attached to your bench to stay set-up.
Exp. Share will stay in Turbo Dark.
Darkrai only needs 2 energy to attack, so attaching to the bench for the third is almost always safer.
You can attach Exp. Shares to things like Shaymin, and suddenly your support mons are helping you do damage.
Exp. Share is weaker to Field Blower than Wish Baton, as you want multiple Exp. Shares in play at a time...
but I think this will be accounted for (one-of an Eco Arm, perhaps).
Wish Baton can find it's way into non-Darkrai decks though, like Lapras, Volcanion, etc.
I think it will be played... it's just not... as game breaking as some of you may think. Haha.