I think it's a new type, which I think will be a Rainbow-type, and I would of thought that even if there wasn't a rainbow in the background. I also think the new legendary Pokémon revealed last month are the same type, plus something additional. The one for Y is clearly part Flying-type.
I would prefer a Light-type, which is something I've wanted since gen 2.
This announcement clearly means a return to having new evolutions for older Pokémon which makes me extremely happy. I didn't think we would see a new Eevee, but I was hoping for one. I hope we get a second one, but I doubt it. I don't like the look of this one.