There are some changes going on at Epcot, primarily due to the sponsorship money that's coming in from Siemens. The major changes are the announced refresh of Spaceship Earth, the already open update of the Spaceship Earth post-ride area, and the rumored refresh of Illuminations (sponsored by Siemens' Sylvania Lighting brand).
Sure, Disney could market the Siemens changes, along with any enhancements that have been made to Epcot over the past two years (such as The Seas with Nemo and Friends). There will undoubtedly be some pins and other commemorative merchandise.
It remains to be seen if there will be any effort to draw attention to the 25th anniversary of Epcot -- or if Disney Parks & Resorts management has decided that all future marketing efforts must be global (like the silly Year of a Million Dreams). In that case, the 25th anniversary of Epcot is not global enough.
Disney could have used the 25th anniversary of Epcot for a major focus on Epcot -- one that provides temporary and permanent enhancements to the park. If they had, we'd know about it by now because there would now be work going on all over the park.