While Optimus suffers from amnesia, Megatron manipulates him into joining the Decepticons.
They already have the Matrix. It is what caused Optimus to revert back to Orion Pax. I hope we see Jack use the key the way Sam did in ROTF!!!
HOLY **** I TOLD YOU TUMBLR, I WARNED YOU ABOUT THE KEY TO VECTOR SIGMA I ****** TOLD YOU HUUURRR NOW THEY'RE GONNA GO TO CYBERTRON AND GET THE MATRIX **** YEAH GURL I TOLD YOU I TOLD YOU GURLS