It's the 60th. Disneyland has been known to do special things every ten years.
Yes, I admitted there have been some rides that have received upgrades for basically no reason. Disney could have upgraded lots of Disneyland's rides within the past decade, but they haven't. Pan, Matterhorn, Mansion, and Soarin' Over California/Grizzly Peak are one bunch of rides getting upgrades. This hasn't happened since the 50th anniversary, a decade ago.
We shouldn't really count Space Mountain. Disney was forced to close it down and update its track.