Assuming that they can receive and send their money quickly and conveniently with ecash, I speculate that they will never care about the difference between centralized and decentralized.
Would this not hurt bitcoin as a currency? Would this not only encourage bitcoin to be used as a speculative investment? How about mainstream adoption?
People already could spend money quickly and conveniently, central bank coins bring nothing new to the table. The biggest revolution of the recent years was Google Pay, it freed people from the need of carrying their payment cards, risk losing them or forgetting them at home, managing multiple cards, etc. If consumers can already pay instantly with their smartphones, why should they switch to a new method that offers the same, but is not widely adopted?
Central bank coins need to become big enough to be viewed as serious competitors of Bitcoin, until it actually happens it's to early to worry about them.