My retailer said that while the motor is very similar, it’s doesn’t quite fit the same. There’s something about the bottom of the motor that makes it not backwards compatible. That being said who knows what kind of retro-fit kit they might come up with in the future. My understanding is that it IS NOT backwards compatible. I do not work for Specialized and I do not work in the industry. I just ride a lot, buy new bikes several times a year, and don’t have much else to worry about.
I don’t want to steal Specialized’s thunder but I will say the new bike and the Fuel EXe are definitely competitive. One is a better value and one I suspect is a better bike altogether…. but both are really good. I’m dying to hear what the online reviewers say.