Yep, Tesla investors have nothing to fear here. It's good for the market to be comparing Tesla and Nikola. I am confident that most investors will appreciate what Tesla has accomplished already and what challenges lie ahead for Nikola.
In my view, the biggest miscalculation that Nikola is making is that hydrogen-battery hybrids only make sense if there is no way for the economics and performance of batteries to improve. So every advance of batteries makes hydrogen obsolete and a little less competitive.
So fine, let investors buy up those NKLA shares. I expect Nikola will evolve to offer BEVs only or fail. Of course, other's could argue that hydrogen tech will also gain efficiencies with scale too. Indeed, Nikola has placed such a large order for electrolyzers from Nel that is it singlehandedly driving the cost of electrolyzers down about a half to $350/kW. This has enormous value for enabling a cost effective low carbon economy (even if no road vehicles use hydrogen in the sustainable future). So some of Nikola's hydrogen investments could payoff even if all of there vehicles become BEVs. Heck, even Elon will need cheap electrolyzers to get home from mars. So technological competition is a good thing, and Nikola could find its way in the long run.
Anyway, as a Tesla investor, I don't feel threatened by Nikola in the least.