@renard @jwildeboer battery degradation slows down over the lifetime. Although this probably depends on the chemistry.
BEVs typically have lower maintenance, so I don't see why 20yr can't be matched. If (e.g.) 70% State-of-Health is acceptable 20-years in, i guess it's still a viable car to drive.
However, I'm not sure why "20 years" is a metric to hold up against. Is that primarily a financial consideration? Worded differently: Would you buy younger for the same price?