I think I'd take a whack at turning text into fog then reversing the animation. I think animating a combination of distorts and a translucent material could turn your text into broken bits of smoke...I agree with Tunesy that at that point you would "sneak in" some proper 4d clouds and "sneak out" the remains of the text. Actually, I wonder if you could do something with 4D clouds and a transparency map, too. Another thing I wonder is, as far as I know the elements going into a boolean intersection can be changed freely up until you "freeze" it by exporting the result. So you might be able to boolean intersect your distorting text objects with the still-moving cloud...