There's no way Boeing will be going "under" just because 1 model of their planes is impacted

737 MAX is impacted but there's still 737 NG which doesn't have these issues

And then there's 747, 767, 777, 787 which are still under production

This is just the commercial plane side of the business, there's the huge defence side as well

Finally, Boeing has been playing this game a long time, very well connected in gov and congress, and its business impact many states and employees. Boeing is basically too big (and too well connected) to fail; even in the worst possible case, they'll probably get a bailout.