maybe its not lava, but really hot Jello.
personally ever since i read the ANH book, i've always thought of the lava story being abit silly... but then all the book says is 'anakin fell into a volcano' or something like that. whereas i'm hoping the movie will tell us more than that.
i do think palpatine will have a hand in it... i mean, ok so he can't fly, but maybe he has some other means to help anakin.
we will see.
as Rhett said, theres no point arguing about it until we know the specifics