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.
It'll bifurcate as a market. Nice, collectible, lesser used ICE vehicles will go up in value, for collectors that can still afford to operate and own them. It'll be a wealthier person's hobby. For everyone else they'll have very little value and most of the market will become far more burden than it's worth (because there will be increasing environmental costs associated with operating them, selling/buying them, registering them, and disposing of them).