We keep hearing that the big global automakers are gearing up to challenge Tesla (NASDAQ: TSLA) with premium electric vehicles of their own. We've already seen one, the impressive Jaguar I-Pace crossover. But what are the others? And when will they arrive?Below you'll find the roadmap, a handy-dandy guide to when we can expect the long-talked-about Tesla challengers, upscale battery-electric vehicles from established automakers, to actually arrive at dealers.