Pure speculation here butcould Unicron take a human host? And what would Jack do to prevent the chaos bringer from manifesting...?
I have to seriously ask, why
would Unicron possess Jack? To infiltrate the Autobots perhaps? That could make sense I guess. But I honestly think that he wouldn't bother inhabiting a puny fleshling. I mean, they're kind of soft, squishy, and weak. The exact opposite of Unicron. Especially when he has a much larger, more durable and intimidating body to use anyway. Unless they're going to make Unicron a cunning strategist who borrows Jack's body for a short while to do something that doesn't consist of killing, smashing or eating, I have difficulty seeing that happening.
But then again, I'd like to see a more strategic side of Unicron myself, if only because it would make for some degree of character development. I've always liked the idea of the character myself. He has a good background, (even though it's full of plotholes)
a neat character design, cool toys... and is flatter than a squirrel run over by a monster truck. I don't expect (or really want) him to be a relatable character of course, or even deep, considering he's meant to be an embodiment of chaos and yada yada, but I wouldn't mind a little more substance, you know?