Unless battery technology takes another quantum leap I feel like electric motorcycles will just be suited to commuting, or niche purposes like kid’s or beginner’s bikes.
The Stark Varg is being developed as a competitive MX bike – supposedly it can complete a Pro 30-minute plus 2 moto. Here is a Varg Ride Review from CycleNews.
So I guess if a Varg was legal for MX competition you would only need a spare fully charged battery to swap in for Moto 2. Oh, and just forget it if you want to enter a desert, XC or enduro race – those are multi-hour affairs.