Rotating Gamemodes is so much better than keeping them open for 2+ weeks.
And I truly mean that. This game turns to utter shit when Riot releases Featured Game Modes for an extended duration - it's splits the queues up, that results in lower quality games in the regular queues, not to mention the featured gamemode itself develops a meta and all the fun gets sucked right out of it.
Who knows, maybe this will pave the way for Riot to combine gamemodes.