Tesla has reached enough scale to be more or less sustainable (in the sense that they don't need to be posting losses anymore), and I'd imagine they can continue to grow, if more slowly, without the rapid expansion of battery production capacity that this story is about.
But the great aim behind the gigafactory (at least, how I read it) was to drive battery cost down very aggressively, that is, working on the supply-side economics. This would then make EVs (not just Teslas) accessible to more people sooner, without all the subsidies (which have been a demand-side hack that didn't even work very well). If this means a slower clean transition (and I think it does) that's a sad outcome.