As far as specifically 3D. Those I got for my own enjoyment and with 3D almost gone not many will be wanting those. I think James Cameron screwed him self waiting to long for Avatar 2
As far as 4K, I think anything with a 4K is going to be more desirable than a standard BD. For example after getting the John Wick 4k three pack I've decided to sell my Wick NM 2&3 Although primarily just to make room. The practicality does make a difference to me even if I plan to keep it sealed. I'm hanging on to number 1 cause I love the movie and the slip.
Will the value of our collections hold up over time?...depends how long. Not many want a movie they've never heard of. I think some editions will hold Thier value, some shall not.
I mostly keep about %90 of mine sealed because I'm as the point of every new one I get I gotta sell another to make room. In addition to that do to the delays between normal plastic release and a special edition, I'm buying it as.....I guess I'd call it a physical representation of my enjoyment of the movie too look cool on my shelfs.
I have started opening some, that I know I will never ever ever sell like for example my BB Alita and HDZ Shazzam. Although to be honest if I had a physical copy of Shazzam already that might have been kept sealed.
Also since it was brought up Physical Media All The Way!!! I freaking hate digital because it's not yours. Your simply buying access to some companies copy stored in a server. If that company goes bye bye so does your movie. Plus you can't watch digital anywhere. Some companies like Vudu are better about having thier app available on everything but unlike a bluray which will play on any player (in your reigon) you gotta have the app and an account. Also an iffy internet can be a problem if you're streaming 4k.