According to Bill Hunt of The Digital Bits (who is typically on point with this sort of stuff), Disney will reportedly be suspending the release of any live-action catalog titles on 4K Ultra HD. With the exception of new theatrical titles, animated projects from Disney or Pixar, or Star Wars and Marvel Cinematic Universe projects, the studio has no plans to release further titles on 4K Ultra HD. That's not to say that Disney won't be releasing 4K versions of their catalog movies, but they will be 4K Digital only. I know, streaming is the future, but as long as physical media exists, it will always be my preference.
There are countless Disney titles which haven't received a 4K release on physical media yet, but barring any change, it seems that we won't be adding them to our collections any time soon. Unfortunately, this mandate also applies to 20th Century Fox, which had a huge catalog of classic movies that haven't made the leap to 4K yet, including FIGHT CLUB, PATTON, MASTER AND COMMANDER: THE FAR SIDE OF THE WORLD, ALIENS, and much more. As it stands, the last Fox titles to get a physical release on 4K will be HOME ALONE and HOCUS POCUS, which are due to drop next month. The spread of COVID-19 may play a part in Disney's cost-cutting measure, but Bill Hunt guesses that the studio is more focused on building the Disney+ streaming service. It's possible that Disney would be willing to license out a few of their catalog films to studios like Criterion, Arrow, and Shout! Factory, but that may just be wishful thinking.
One exception to this new move could be James Cameron's movies, as Disney is heavily invested in the director's AVATAR franchise. In order to keep him happy, there's a chance that we'll see ALIENS, TRUE LIES, THE ABYSS, and the original AVATAR hit 4K Ultra HD, but fans have been barking up that tree for some time, especially in regards to TRUE LIES and THE ABYSS, which haven't even had a Blu-ray release at this point.