Good question. I don't know yet, but my guess is, it is basically an up-dated 4.0 V6 that is in our 4th gen, so it is a chain. When we finally see one, just open the oil fill cap, if it is like our 4.0 you can see the chain from the open oil cap.
Also, I would think the 2.7 which is based on the Tacoma 2.7 would be a chain too, but that won't come out till next year.