Maybe, but everyone's developing their own drivetrains and battery packs. Tesla's current advantage is that they've been using them for longer, but that advantage will diminish with time.

Mercedes and Porsche will enter Formula-E starting from the 2019-20 season as part of the marketing push for their electric vehicles:

http://www.fiaformulae.com/en/news/2018/may/mercedes-eq-form...

Mercedes will be in it to win it (as they have done in Formula 1) so they can claim they have the best electric car know-how.