At this point it's probably not even possible to ever reach supermajority for a hard fork increase thus proving Bitcoin is in fact decentralized. Perhaps the only thing that would get everyone on board was a global ban on physical cash, then the only way out for financial privacy would be Bitcoin, at this point it would be an organic demand for a block space and maybe there would be supermajority reached.
Even in that case, creating an "
evil" soft fork could still be better than hard fork. But I guess that something like an extension block could be a better solution, because then you have to/from transactions on-chain and everything else can happen inside this additional block, that can be visible only by upgraded clients and can be for example 1 GB in size if needed.