I made a slight error going from memory. IMAX 70mm is a little over 11k. Film has about 80 line pairs per mm of resolving power and the IMAX frame is 70mm wide. 70 x 80 x 2(line pairs, not lines) = 11,200. However, film is an analog system with a non-fixed pixel grid so it can truly resolve at this level. Digital systems have to have twice the samples of what they can resolve so a 4k system can only actually resolve 2k worth of detail.
Standard 70mm (non-IMAX) is about 8k.
Even with my mis-memory, the current IMAX film has significantly higher resolution than the 4k digital will. As far as the dust, I've never figured out why they have such an issue with it at Soarin'. I assume they have the same particle transfer rollers that normal IMAX theaters have (had when they were film) and they never had an issue. They should also have the same dust clearing system in the aperture. Maybe the 48fps rate makes the film run too fast to get the dust off?
Old school Disney would have worked with IMAX to create a specialized 8k or 12k setup using multiple projectors precision aligned and calibrated to produce an image that is equal in appearance to the 70mm film and better than any other digital projection out there. Just throwing a standard 4k IMAX projector (which is really a Barco projector) in there is something that anybody can do.
See my comments above about resolution. 70mm in motion and projected is very different than a frame of 70mm film being analyzed for resolution.
Re: the dust - only Anaheim got a clean room. EPCOT did not. This is another reason why the 4K solution will be a better fit for Disney.
There is magic in celluloid. There is no doubt about it.
Cinefiles get very passionate about their film.
If you've ever seen a great quality film print on a great projector, then you can certainly appreciate it. Seeing a Star Wars movie at the Stagg theater at Skywalker Ranch is something that leaves an impression on you.
For most of the world, that possibility isn't a reality. Seeing a summer tentpole film under ideal circumstances is something that very few of us have ever done. Your local multiplex could never live up the standards of the flagship theaters that actually employed people to properly care for the projection equipment.
This is why the digital revolution has been so great for the theater industry for the consumer.
It use to be if you wanted to see the new blockbuster, you better get to your local theater in the first few days of the film coming out or else you would end up watching a dusty, scratched, patched up reel.
Now with digital projection, every showing is as good as the last.
Is it as good as it could possibly be under ideal circumstances? Nope; but, it's a whole lot better than what 99.5% of the world ever got to see.