In an interview with Variety, Zuiker gives us the best love letter:
Without giving too much away what is the most important bit of closure that you’ll offer your die-hard fans?
This is the Super Bowl for (Jorja Fox’s) Sara Sidle. She’s applied for the directorship of running the lab. This is the one incident that brings back Grissom, and we see her being mentored by (Ted Danson’s) D.B. Russell. This is a case that paralyzes Vegas. One of the big burning questions of the finale is where (Grissom’s) heart will lie. GSR usually stands for gunshot residue but in this episode it stands for Grissom-Sara Relationship.
I expect a lot of Sara Sidle, folks.