CephFS (which is a distributed file system) is orthogonal to XFS or BTRFS which are local file systems. Since Gluster is providing a file system solution at this point, that may be the reason for the de-emphasis. However, Gluster is not a parallel file system, and Ceph is much better suited to fill that role. So I suspect CephFS will continue to be developed, if anything to compete against Lustre, PanFS, GPFS, etc..
Why do you say that GlusterFS is not a parallel file system? Certainly it is by the common definition of "file system that spreads data across multiple storage nodes."
That's because (a) CephFS isn't ready for prime-time (according to every talk I've seen at linux.conf.au in the last two years) and (b) the early push for btrfs as the underlying storage for Ceph has faded in favour of XFS until they're happier with the state of btrfs.