Walt Disney World has started to release some minor details on how it may commemorate Disney's Hollywood Studios 30th anniversary:

Quote Originally Posted by Disney Parks & Resorts
Also, 2019 marks 30 years of magical movie moments at Disney’s Hollywood Studios, so to commemorate this special occasion, on Jan. 18 the park will unveil a new 30th anniversary logo. There will also be new ways to interact with The Incredibles (you’ll get to meet Edna Mode at her new super-suit gallery!) and Mike and Sulley from Disney•Pixar’s “Monsters, Inc.” You’ll also want to experience the new “Disney Junior Dance Party!” featuring Vampirina, Doc McStuffins and other favorite Disney Junior characters having fun in a high-energy live show.
It appears that the additional entertainment announced for 2019 may be the extent of the in-park celebration, but one could safely expect that the new logo means new anniversary merchandise.

It is unclear if the park is planning any event or commemoration closer to (or on) the parks actual anniversary on May 1, 2019.