I think for mass adoption another coin will have o be the base to trade against like tether(which is experiencing problems) or UNY(which is rebranding) These stable coins will make crypto more attractive to many.
A stable coin is all well and good for use as a currency but it still should not be pegged in price to something else. Bitcoin will never be used as an adopted currency in any country. It will be a store of value which is also usable for payments.