There's a long list of things that could be added. After all simulating real life is damn complex!
I guess the dream of all of us, the dream of the modders etc, would be an AC 2.0 that just adds features to AC. I am sure everyone of us would be glad to pay a full game price for that update. Wow! Rain and Night! Driver swaps! Loose surface! Chassis flex! Track objects animation! Rolling starts! And I can keep my 300 cars, track mods, awesome apps! After all AC is today even more alive and kicking than before, and I am not tired at all of it. The thing is that no one wants to re-start from scratch especially if what you already have is good and/or you have spent thousands of hours developing mods, rigs etc. And it's way too early to declare AC a thing of the past.
The sad reality, though, is that you cannot add features to the graphics core or to the physics core without breaking compatibility with the old stuff. I guess that even developing an AC 2.0 Kunos will have to use a part of the resources to develop tools to convert mods from AC to the new title. The other challenge will be the timing. If they stop developing AC (no new features, no new DLCs) they will have no new income until they have the new game ready. And I guess this cannot last for too long. So it looks like in order to be quick enough they will have to repeat the AC process: write a new core, develop tools to convert stuff from AC, then publish the thing in early access and continue development of new features. The risk is finding yourself in the rF -> rF2 situation but I hope they can learn from that experience.
