She's Optimus Prime:
Saldana is smoking hot, super confident and has some of the same imposing physical presence as the departing Fox. Plus, with her blockbuster experience from Star Trek and the mighty Avatar, she knows her way around a green screen.
Wrong like Megatron:
Despicable though it might be, by Hollywood standards Saldana may be too old to play against Shia LaBeouf, with her 31 and he still just 23.