Movie premieres in L.A./Hollywood (and
Disneyland) are usually a week or two before general release, it's part of their big promotional run-up to generate buzz before the opening weekend.
For the Pirates films, DL premieres were invitation only (parked closed early), red carpet affairs and they set up bleachers at the river days ahead of time (which shut down things down) and placed the screen where Fantasmic usually runs on the island. But most Disney premieres in the L.A. area are at their theater, The El Capitan, in Hollywood. With the Lucasarts connection, there is always a chance the premiere may be in S.F. instead.
I expect you'll see promotional ideas and a sneak peek (Tomorrowland theater?) in the park for weeks leading up to the release, and maybe some same-day promotion in the park itself (mini posters are popular for these sorts of things)...but not a premiere for the public. Of course, they announced the big Season of the Force as an "early 2016" promotion at both resorts at
D23 and new footage in Star Tours for the new movie.
The movie will certainly be playing at the AMC theater at DTD, and tickets will go on sale months ahead of time.