A new proposal has been accepted to be included in fedora 18 that will allow software updates to take place while the system reboots. This decision is taken so that some critical system updates take place in a minimal controlled environment.
Often it happens that one may update an application while it is still in running mode or some disk operations are taking place. This may lead to inconsistency of system files and libraries. To avoid this, GNOME PackageKit will download the update packages and store then in a specific place. An option will come in the system menu -"Restart and install updates", choosing which, the computer will restart and complete the updates in a safe and controlled environment while rebooting.
As updating a system is user's choice, normal "Restart" option will also be available in the system menu and user will choose to install updates when he feels. This will not stop critical updates from installing online using yum, as this is only being implemented in GNOME PackageKIt. Also other desktop environments/GUI frontends will remain unaffected.
OfflineSystemUpdates of important OS components while rebooting is already 85% complete, though its still unclear what will differentiate OS Components from other applications as all of them are packages. Adding extra metadata to differentiate them is currently being thought of.