At some point, a stock can get to such an atmospheric price that there is no way that the company could possibly grow to generate enough earnings to justify the price - Cisco in the per-Millenium boom is a great example. I don't think Tesla as a strictly car manufacturer could outdo the now-lean American car manufacturers or the foreign ones for that matter either; these companies will respond to an increase in demand with a comparable product, and could certainly match Tesla with factory machinery investment.
However, there are rumours that Tesla has made a quantum leap in battery technology, both in terms of energy storage per unit volume or mass and the cost of such energy storage per unit energy, and also a super advance in longevity, like a million miles!
Such a huge leap would really shake up the cost-of-use of electric cars to be the clear winner vs. the ICE, and Tesla's patent on this technology would allow Tesla to license its use for ALL manufacturers.
That said, a lot of other folks are doing research, and once a different technology (i.e., "different" in the sense that another patent could be issued for it) gets invented, the value of Tesla's technology would get, relatively speaking, wiped out.
As for myself, I am a believer in "reversion to the mean", so I go for value stocks trading at a very low P/E ratio that could get into whatever business line gets demand., while watching out for such low-P/E-ratio stocks that could get flat-footed, like Kodak was when digital camera came out.