Interesting, I just checked on mine as I have for the past week or so.
At first it said "no updates to install. last checked ." and
then it flickered and showed the download screen for the new one. Either
way it's installed and working now.
I'm having the same issue as well. I recently got a 2nd Chromecast with
Google TV 4K and it says there's no any update available. My existing
one had no issues and pulled the update when it was released.