As promised, I talked (via PM in FB) with EA Matt about the ELO ranking in RR2, and asked if there is anyone left to get in touch with regarding that aspect of RR2.
He finally got back to me on it and informed me that there's really no more dev going on with that app, but he was able to talk to some of the original developers (who are now still at FM), and they offered this history of ranking in RR2...
The older system of grinding for rank wasn't particularly loved as it just required a lot of hours to be put into the game, as opposed to actual execution of skill. So that's when the ELO system was introduced, which as you know has also returned for Real Racing 3. The main reason for this system is that it supports a competitive eco-system, rather than allowing noncompetitive grind, and we really dig that.
As for when it came down to the future of the ELO system, essentially the feedback was so mixed that there wasn't a firm reason to go in either direction. From the feedback we saw, some players really loved the ELO skill system, some preferred the grind, and the decision was made to leave it as is instead of switching yet again. So, not so much of an experiment left in the game, but more the last iteration on multiplayer.
Hope that helps!