Updates to the newest LTS are usually offered when it hits in this case 16.04.1. This is done because LTS releases often run in production enviroments and they want stable releases.
To have a check you can simply do from terminal
this will check if there is an actual release. If yes run the command
or respective if you did
sudo do-release-upgrade -d
-d will get you a development version which can be an option to get the upgrade going just make sure youre getting the 16.04 and nothing else from that branch.