When released, how will this card alter the metagame?
Alter the metagame...I really have no idea. It's an interesting card, and while I can see it having potential with some weird juniper/ultra ball acceleration, I don't think it'll change how we play anything. The ability is flippy, and the damage output is not fantastic when it needs so many (most likely) special energy piled on it to do serious damage and hit almost nothing for weakness. Meanwhile, Empoleon can take it out with only 8 total Pokemon in play, which isn't all that hard to do.
What decks will it see played in?
I'm imagining some sort of acceleration with Beautifly or Terrakion-EX, or something similar, but I can't see it being all that fast or strong. I've seen an idea being tossed around where you use Phoenix to revive Ho-oh as some sort of acceleration for the rest of your team, but...meh. In the end the attack is an incredibly nerfed X-ball, which not only can't use the opponent's energy, but requires a variety of energy in the first place.
How will it be played?
Without Junk Arm and Shaymin UL, it's not all that easy to use Phoenix, attach energy, move it, and SSU the Ho-oh back to your hand, or something similar, as if that was a simple plan in the first place. I don't feel like Ho-oh will be making too much of a splash this year, with an attack that needs 4 special energy, or 4 different basic energy, just to hit 100. I do think, though, that it'll remain one of those weird fan favorites that people keep trying to make work.
Rating: 6.5/10
The card isn't necessarily bad, but the attack is outclassed by X-ball, the weakness is dangerous with the rise of Emploeon and possibly Keldeo in a few months, and the ability, as cool as it is, doesn't have much to offer in terms of an efficient form of acceleration.