It is already illegal for businesses in Switzerland not the accept cash [1]. In fact the law specifically states that you need to accept up to CHF 100 in coins and all bills (including the CHF 1,000 bill). The issues is there is no penalty define if you don't and some businesses have decided they don't want to accept cash.
This vote however wont fix this, all it does it force the SNB to continue to make cash available in the constitution when the SNB itself already clearly stated they have no interest in getting rid of cash and it is currently in the law. There was pressure from the EU for Switzerland to get rid of the CHF 1000 note but they didn't.
If no one accepts cash the vote is mute. At least some should be forced such as food and clothing stores. Stores that are not 100% online.