You'd need to amass 50% of the shares to kick out the founders. That'd be impossible for a hostile party to do if Stripe IPO's because they wouldn't release anywhere close to that number of shares.

The only way to kick out the Collison's would be for the VC's to do it. They currently own 80%. It's easier for the VC's to do that if Stripe stays private than if Stripe IPO's.