DNF is expected to replace Yum in Fedora 22 but that is still subject to change.
That hint of doubt worries me. I'm not currently using Fedora. I've used it before, and found that Yum is just too slow - takes at least five times as long as Ubuntu or Debian to install a package. It's been a showstopper for me.
But overall I like Fedora, and I'm particularly attracted to its security. Selinux by default - that's what I want. Supposedly, one can install Selinux onto Debian, but my attempts to do so haven't gone all that well. Selinux is complicated, and someone has to do the dirty work of setting up policies carefully and testing it with various packages. Red Hat/Fedora has done that - kudos to them.
So I was seriously considering using Fedora as my main desktop OS, contingent on DNF (or something equivalent) becoming the standard packaging system. I had my hopes up that Fedora 22 would be my future - now I'm a little uncertain. Bummer.