The fully fitted part of the game is the RaceRoom Experience part, there you can do whatever with the content you have with the features the game provides.
The experiences are bound by the rules and content of that given experience, and on the question if they will always be updated to the latest, the answer would be most likely not all the time.
F.E. I doubt we will implement pitstops in DTM 2013 Experience, its too much effort, and seeing that all DTM content is now available in the Raceroom Experience, with all (and more features, with more to come) there is no real need to.
Edit:
The RaceRoom Experience will have access to all features, so things can be mixed and marched to your liking in the future. As stated below it makes no sense to update all experiences with all features, f.e. pitstops in WTCC experience won't be there, since they don't happen in real life either. But when playing WTCC cars in the RaceRoom experience you can do longer races and pitstop if that is what you like.