The car glut will be in non-EV's. There are a lot of buyers who don't care what type of car they have, and will buy an EV the moment they get cheaper than a gas car - therefore sucking up any glut.
They're already cheaper, so I think it's primarily range anxiety that holds up most people from making the switch. Once you get comfortable with how the EV works and trust that it isn't lying about range, it's an easy choice. Especially so for anyone who keeps their cars a good long time.