You might be right for the high end (the Bentley example), but the middle/lower end of luxury isn't that interesting as a collectible, cars like a 5 series BMW, or Lexus LS, and could really drop in value.
Seeing how manual transmission cars from the mid aught's are demanding a massive premium (like 100%+ on 1,3, and 5-series), I could see in 2045 ICE cars demanding a premium. Manual ICE cars even more so. But that's assuming they aren't projected to be illegal/heavily taxed by then.
Yep -- already they do, speaking as someone trying to find a manual BMW Wagon.
The supply is already gone and has been for a while. The other comment in this thread on ever-smarter (cloud connected) cars too means that the market for not-cloud-connected cars is going to continue to increase too.