Sony has announced via Twitter that system update 2.03 for PlayStation 4 now has been released (we've already updated our consoles). Unfortunately, there aren't any new features and the description is the very same as for the last update and it "will help improve usage of some applications".
Most likely it fixes some of the problems users have experienced since the release of system update 2.0 in October. At least now you know why you're being prompted to update your console.