There hasn't been a system update since December 5th. The most recent game updates were MK8 and Sm4sh, though, so maybe that's what you're thinking about. And yes, it's still perfectly safe to update
That's weird. I just set up Open DNS to block updates around Thursday or Friday and the next day a red x appeared over download management. When I checked it, it said a system update had failed. So if one hasn't released since December, why is that there? Strange...