1) It showed Shisui alive with 1 eye missing, saying Danzo took it. He then willing gave up the other eye to Itachi. Later he was found dead with the suicide note, knowing Itachi and him seemed to be BFFs.

2) Danzo has the first's cells, that would explain why it took a few hours to reactivate the Sharingan instead of a decade.

3) Looks like Nagato is sucking the chakra out, giving him more fuel. (*NOTE THEORY: This could also explain with only one to control, Kabutomaru is able to exert more control over him instead of splitting it to the both of them.)

4) Guessing Naruto will have to go back to Sage Mode and turn him to stone, effectively sealing away Nagato as a statue.

Itachi was always pretty bad-ass-mofo, but this just shows how calm and collective he's been has all been part of his plan. Knowing what we've seen, I would put it past him to just release himself once this war is over.