blog entry on journal by the primary author of rsyslog

It was given the name fallback to make clear it is not the standard mode. Intention from the start was to keep it for the entire GNOME 3.x. However, amount of maintenance it needs was severely underestimated. This coupled with low usage (though impossible to measure) is the reason the maintenance might be given up earlier. Still not decided though.

And if you want it more official:
http://mail.gnome.org/archives/release-team/2011-November...

Please note the lack of reply on that :P