Other events outside the technical 60 years that could be in second movie:
Gandalf tricking Théoden into giving him his horse shadowfax.
The dark riders asking Dain and the dwarves of the lonely mountain about Bilbo/Hobbiton location.
The attack on Mirkwood by Sauron.
Gandalf meeting Thorin in the Prancing Pony, which set the whole thing into motion...
“A chance meeting, as they say in Middle Earth.”