Looking at this article from LWN.net, it appears the default filesystem for RHEL 7 will be XFS. XFS was the default filesystem from Silcon Graphics Irix Unix from back in the day, and I believe one of the first 64 bit filesystems in widespread use. It’s been open sourced for a while and has been included in the linux kernel for a while now. Also, the desktop version of RHEL 7 will default to the Gnome Classic mode, not the newer Gnome 3.0 interface. That should make many people happy who dislike the newer interface. I’d imagine all of the changes will make their way into a future release of CentOS and others.