Telltale generally waits until closer to release before showing stuff off.
All we have of Back to the Future is some concept art of Doc and Marty. No trailer. Not even any screenshots. Just the concept art. Even Poker Night at the Inventory, which can't be more than a month away, has nothing but a few screenshots. (It technically has a trailer, but I don't count that since it was incredibly teasery and predates the official announcement.)
We won't be seeing any Jurassic Park stuff for a while. Be patient, though. It'll come.