CP2077 development and expansions are essentially dead.
The game isn't, there is tons of replay value, new builds, different choices, or just going full chaos cyberpsycho. But development is dead because Red Engine is dead. And that's a good thing.
The move to UE5 should be a positive for the future of CDPR and their games. I know a lot of people want to see CP2077 continue, but honestly they told the story they wanted to tell. Making Cp2077 an endlessly updated platform doesn't make sense, the same way you wouldn't do it with TW3. It's not live service its a single player RPG. A great one but those games always eventually have an end.
Besides making another expansion takes people, money and resources away from the next witcher game or the next cyberpunk game. Cp2077 should get a few more bug fixes and some small-scale continued support, maybe even 1 or 2 last little surprise content updates like 2.11 had which most people did not expect, but moving most of the team on to the next project is the right move. As for your point about another expansion showing "Work in Progress" on the sequel and giving people insurance/sales pitch for the sequel. Well they're two completely different game engines, so it wouldn't be a 1 to 1 comparison anyway. Anything a hypothetical second expansion or surprise update would have does not necessarily translate to being a feature/mechanic/etc... in the next game because Red Engine to Unreal 5 are different systems.