There are certain MCU entries that are guaranteed to look amazing (recent entries like Civil War that were actually mastered in 4K), though the majority of the MCU were mastered with a 2K Digital Intermediate and are likely to be upscaled on UHD. They'll still benefit from the wider color gamut and high dynamic range, but they won't have the sharpness of native 4K titles.
I do hope that Disney feels certain titles are deserving of a total overhaul, creating new 4K DIs in the process. The first Iron Man is one title I think deserves such treatment; it's a modern day classic, and one of the MCU's best entries. That one was shot on 35mm, so they'd need to go back and give the original elements a new scan and rebuild the film. The CG elements should be fine upscaled (the vast majority of native 4K features still use CG upscaled from 2K renders), but the film elements really would benefit from a new scan.
There apparently are 4K versions of the original Star Wars trilogy floating around Disney somewhere, and I imagine we'll see those eventually. The only downside is that they're the Special Editions, although it's been confirmed that all the original material exists to rebuild the theatricals if Disney is ever so inclined in the future. Those are the only versions I'll buy, personally, so I'm hoping somebody eventually sees the wisdom of offering them. If Ridely Scott can put out 5 cuts of Blade Runner in the same set, I don't see why we can't get these.
Edited by TM2-Megatron, 07 July 2017 - 11:31 PM.