As you may know, the Fedora developers started work at a new RPM package manager, called DNF, which is a fork of yum, and uses the libsolv library. It has been integrated in Fedora 18, but it is still under testing. It should replace yum only when it will be stable enough to do yum’s tasks successfully.
It has been updated to DNF 0.4.6, which comes with support for new features, including: “history undo” which enables the users to revert all the package transactions, “group summary”, Python 3 optimizations and some bugfixes.
In order to set DNF as the default package manager, the Fedora developers will need to switch to Python 3.3, for the future systems.