I work with a couple of organisations that have been advising public institutions on their investigations into CBDCs, and the entire timeline of FedNow development took place after CBDCs had initially been conceptualised. CBDCs became a mainstream concept in 2016 when the Bank of England started discussing them publicly. The Faster Payments Taskforce report (which was the basis of FedNow’s design) came out in 2017, and the Fed announced its plans to start work on FedNow in 2019. Many advanced economies announced plans to start seriously investigating the use of CDBCs in 2021, but they’d all been discussing the concept for years at that point.
I don’t know whether the fed’s investigation into CBDCs will result in it adopting one. But FedNow has been designed in such a way that it could easily be modified to support one. You’d just have to implement a version of it where the allowed participants were everybody who’s allowed to have a bank account, rather than only banks.