The end-of-life for CentOS 8, according to https://www.centos.org/download/, is going to be 2029-05-31; however, RHEL tends to add a few extra years of extended support beyond that. According to Wikipedia, the longest extended support so far was around five years, which would get us to 2034. And people often use operating systems many years beyond their end-of-life.
Keeping in mind that XFS is a filesystem format, it's not hard at all to imagine a filesystem created in CentOS 8 and/or RHEL 8 still being in use when 2038 arrives, even if the operating system was already upgraded to the next major version.
Keeping in mind that XFS is a filesystem format, it's not hard at all to imagine a filesystem created in CentOS 8 and/or RHEL 8 still being in use when 2038 arrives, even if the operating system was already upgraded to the next major version.