Interesting... I would never announce a manager's departure before the end of the season, it would mean to players that they can coast to the end of the year without expectation. It has certainly worked that way, most of the time, in football.
It may of course have the opposite effect, if players are looking to keep roles and will need to put in a shift to do so. Time will tell.
Nonetheless, the announcement has been well handled and allows him to leave with his head held high.