I think its not need long time for electric bike  replace fosile fuel bike, if you not believe me take a look at :
                                       BRAMMO EMPULSE R

BRammo  Empulse R powered by water cooled  ac permanent magnet motor give you outstanding performance ,it can run until 160 kmph . If this bike full charged it can travel until 200 km. The BRammo Empulse R  price is at around $15000,  maybe is still too expensive, but i am sure  this price will lowered in future time because the price of battery being used in brammo Empulse R become lower, caused by the increase  of battery production effeciency.