Isn't BMWs new battery production at a similar scale? The main difference between Tesla and big manufacturers is not necessarily factory size but marketing.
The gigafactory is huge as one building. As a car manufacturing plant it's not that big, compared to the cities that some of the other manufacturers have.
In short, odds are greater that Tesla will exist in a post-combustion world than established automakers.
I mean look at the battery supply chain alone. For them to deliver at Tesla's scale, they'd need enough batteries, which, right now, would require major investment a la Tesla's Gigafactory: which is set to produce more batteries at one factory than the entire world's current output... all to support Tesla products.
At what phase are the established automakers in their infrastructure investments? They're all years behind. And I'm afraid they won't catch up.