Skipping 6 - Jumping from 5 straight to 7

Thursday eve: 6pm (?)

We have been building our site for a two years. By the time we are able to allocate resources to a Drupal upgrade, 7 will be good to go.

How do I make the most of my resources and just jump to 7 ?
What are the key challenges we are going to face ?
What work can we skip ?
How can we share the load and make skipping easier for everyone ?