Everything is possible. I think it was @Druddigon who said that there were speculations about that. Thoughts?
Possibly, but I can't really see any other types for it besides Poison, and I don't really know what it would turn into. But, that'd be kinda neat if they came out with a Water/Poison or a Ground/Poison Toad.
Anything is Possible, SO Palpitoad may get a Branched Evolution like Poliwhril.