So "Mister I never forget a face" Chekov is wearing red in the trailer indicating a transfer to secuirty or enginneering. Let's take the Greg Cox book Reign in Hell, Chekov was a reshirt in security who led Khan and his men down to Ceti Alpha V and helped established the colony. So there you go. It's Khan. Actually Cumberbatch is Jochim and Weller is Khan, hiding in the shadows ala Norman OSborne in 2012's Amazing Spiderman.