There are two schools of thought:
1: rF2 will essentially be abandoned. Much like AC or AS(I can never remember the initials for Automobilista) It will continue on Steam, they will support the online content and possibly one more quality of life type update, but very little more will happen. Look at Rieza with their track/car pack that is sold via the rF2 store. Rieza had to hire an rF2 modder to update the track graphics because ALL of their resources were going into AS2. And even then, they can't get the updates redistributed because S397 also has nobody available to work on an item that will bring in zero additional income.
2: LMU is moving further and further away from the rF2 code base so it would make very little sense to try and back-port content from LMU. Sure modders may be able to rip the 3d models and such, but the Hybrid features will probably never reach rF2. It will essentially be abandoned.
or
3: It will will be abandoned. Users will still be able to host races, and such as long as Steam is paid by S397 to distribute rF2. But no further coding will be addressed.