Bolin will Lava bend.

[Cabbage]

Not possible, only Avatars can use more than one element, besides advanced earth is only metal bending nothing else. He had always wanted metal bending and there is no lava bending in the whole Avatar series ..........

It's been confirmed that Gharzan was lava bending by Bolin in the last episode, it's probably just an extremely quick rotation of the earth within the Avatar-verse...