If the coin creation method is changed, the ASIC owners have nothing to say.
Bitcoin uses proof-of-work, and therefore the majority of the hashing power decides. Why would the current stake-holders be so stupid to switch to a system which is unproven and where there economic advantages, i.e. their capital investment becomes worthless? That makes no sense whatsoever. Coin creation in Bitcoin doesn't arbitrarily change. That's why its a solid system. If such changes were possible Bitcoins would be worthless. All of this should be obvious to anyone who wants to understand why Bitcoin works.
It is precisely BECAUSE of what you described that if any PoS would ever be implemented by anyone based on Bitcoin blockchain, it will be a fork, or an altcoin, and not Bitcoin. And therefore you and all of the ASIC miners will have no say in the process, because it has new rules.
If people see that the intruder is gaining in value and Bitcoin is losing it, they may try to get extra share of the new coins by selling their Bitcoins, hastening their demise. The original Bitcoin proponents will only lose, though, if they have sold the spinoff, thinking that it is worth nothing.