Different more stable alternatives will take its place as basemoney. Bitcoin is on the best way to sink into obscurity - this hardfork just speeds it up.
It is not the job of "base money" to be stable against other currencies. Base money doesn't give a f*ck what its value is or even whether it has any - its job is to function as a monetary medium of high integrity which means resistance to counterfeit, fungibility and tranrsmittability.
In a physical market, many things fulfill that role. In an electronic platform only cryptocurrencies can fulfill that role - in other words they can be transmitted on an electronic platform without the need for a counterparty (bank).