Cash in the only practical anonymous-when-you-need-it-to-be way to pay still.
Don't let it die until we have alternative suitable anonymous and un-blockable-by-cyberattacks (eg. "it must still work while the internet is down") currencies!
(Note: no, we don't have yet, all current crypto currencies are "barely working prototypes" at best, all of them have issues that still need ironing out! Bitcoin itself is like a proof-of-concept-pre-MVP that got "rushed into production". And the blockchain itself... we NEED to have a way of fully erasing history from it, like paper money do, we don't yet know how to do that while keeping the nice properties of blockchain... all these are open research questions, Satoshi only made the first baby step!)