It's easy for Tesla to make these promises when the first Roadsters aren't expected to ship until 2020. This gives it plenty of time to tackle the challenge and figure out exactly how much power they can wring out of this design. However, an even faster car is more plausible than it might seem. The key to the Roadster's breakneck pace is cramming a 200kWh battery (twice what a Model S P100D has) into a compact body. It wouldn't take a dramatically larger power pack to see substantial gains, even considering the added weight that usually comes with bigger EV batteries.
As it is, even a modest improvement could make the Roadster tough to beat, at least in some situations. At present, the fastest factory 0-60 time outside of Tesla belongs to Dodge's Challenger SRT Demon at 2.3 seconds, and that's a stripped-down single-seater. There are cars with higher top speeds, like Koenigsegg's Agera RS, but they're either no longer in production or aren't as quick to hit the 60MPH mark. Provided the Roadster lives up to Tesla's bragging, it might only face serious competition once other automakers commit to electric supercars.