IMO, EREVs and PHEVs are actually quite similar. My understanding is that the gasoline engine in an EREV never drives the wheels, whereas in a PHEV, it can sometimes drive the wheels, even when the battery has power. In my PHEV, this only happens at highway speeds and only if I've hit the throttle hard. Otherwise, the vehicle is basically an EREV. Other PHEVs are touchy with the throttle or maximum speed on electric and so end up kicking on the gas engine to drive the wheels much more often.

I actually have a different expectation regarding the popularity of EREVs. I think that for a certain segment, they'll be quite popular because they give the best of both worlds if the maintenance doesn't end up being too much more. They can end up being preferable for people who want to take long road trips without having to worry about charging.