As someone who cut his teeth on motorcycles, I don't think there will be that much crossover between electric motorcycles and eBikes. They're vastly different creatures. No pedal assist on a motorcycle, huge weight differences, huge power difference, all that. The battery needs are quite different too. When the motorcycle runs out of juice, it stops. When the eBike runs out of juice you can still pedal it home. You may not like to do it, but you can. I wouldn't want to see a lot of crossover anyway because if ebikes became more like motorcycles we'd have to register them, get insurance, pay all sorts of taxes on them, pay for inspections, all that. I'm perfectly happy with a bike w/ an electric motor that doesn't need any of that.
The motorcycle manufacturers will be very happy about going electric though. Electric motors are really simple compared to internal combustion engines, and you can simplify the drive trains. No need for a clutch, and since electric motors develop full torque at stand still, you can eliminate a lot of the gears.
Your usual Harley rider isn't going to be trading in his bike for one, but the commuter and cafe racer types will be interested. Unfortunately, one of the safety features of gas engined motorcycles will be eliminated. Having those loud pipes lets everyone know you're there. I'm not sure that I'd want to ride a silent motorcycle for just that reason. As a pedestrian, I've almost been run down by a couple of Prius vehicles already.