What Jesus was "about to accomplish at Jerusalem" was his death, burial, and resurrection, followed later by his ascension into heaven. There was still time yet before events would unfold, but heavenly plans were being made and confirmed. When I think of the cross and the empty tomb, mostly I see the cross and the sin of the world that put Him there, my sin that made His sacrifice essential for my eternal survival.
It's interesting that Moses and Elijah seemed to see things a little differently. The word translated as "departure" is exodos