> some of the existing automakers seem to still be covering their ears and singing
Some, but the more common story is "traditional automaker pouring billions into EV production to make up for lost time."
> If Tesla starts suffering mortal market-share wounds, they will still be a compelling acquisition target
More importantly they'd need to suffer mortal market cap wounds. At anything like current prices they're not only dreadful value, they're simply unaffordable. At the moment Tesla buying a large traditional automaker is more likely than the reverse (though maybe not likely in an absolute sense.)
If Tesla starts suffering mortal market-share wounds, they will still be a compelling acquisition target for one of the existing automakers who are late to the EV party-- you get a ready-made bag of patents, supply chain, and designs. You can immediately start building a Model 3 with an Acura or Chrysler badge, and you've got something to ship to dealers in countries with punitive tax regime or ban on gas cars, and a few more years runway to fully adapt the design into a full full own-brand EV.