I doubt the long term effects. The regulars I see are still the same regulars and there is some increased activity of people which already abandoned LFS before. Life experience tells that once abandoned it gets much easier to abandon again (nice those we are back! threads but it's all empty talk).
This Rift hype sure helps though to let the world know that LFS exists and hopefully it provides some new good drivers/racers which stick but I have my doubts they keep/have something over their head. Not at this stage, maybe when a customer version finally gets released.. Its still is a geek device; "try, yes, funny.. OK.. Bye".
What has proven it's long term value is content.. Fresh content always works (if it has some quality). It's not only a road to success in the gaming environment but with basically everything.
I don't really get the irritation, anger, frustration and other negative commenting when somebody questions the release of new content. I think it's not really needed when it's sure that something really nice is about to be released.