I don't know what the car market is like where you live, but where I live the majority of people only buy used cars (because of the lower cost). This is possible because of a surplus in supply of once-new cars. If we're going to get past the tipping point for electric cars, I'd suggest we'd need to see one of three things happen:
1. New electric cars sold at a price point that can compete with the used car market.
2. An increase in popularity in electric car conversions (whether DIY or done by a professional).
3. Wait until the early electric car models trickle down to the used car market.