Lawrence Frost and Gilles Guillaume:

Electric car prototypes and plans are set to dominate the Paris auto show as the Volkswagen (VOWG_p.DE) diesel scandal and falling battery costs persuade executives and investors that plug-in vehicles are ready to go mainstream.
 
 The expected flurry of announcements signals a threat to pioneers of the current generation of battery-powered cars, such as Tesla (TSLA.O) and Renault-Nissan (RENA.PA), who will now have to work harder to defend their lead.
 
 VW is leading the charge, keen to turn a page after its exposure last year as a U.S. emissions test cheat. The German carmaker will showcase new electric vehicle (EV) architecture underpinning a staggering June pledge to achieve annual sales of 2 million-3 million electric cars by 2025.