Luckily we currently have the built-in “feature” of price inelasticity that will prevent Blackrock et al from gathering too much supply without exploding the price.  I see it like an immune function for BTC the asset. ETF issuers also have contractual obligations that somewhat prevent them from acting out.

Is the network itself (ie miners and nodes) at risk? Doubtful.

FWIW I’ve got more hope in the common sense of the community… and even Blackrock itself… a fork like that would destroy the value of the asset and therefore the associated fees. The only people left would be NGU folks / basically those interested in selling for profit in some other currency. In essence a disastrous rush for the exits for all remaining involved.