If Riot refuses to bring back old game modes, just image what could happen to ARAM and TT
They are going to start realizing that these two maps don't offer them anything for their sheer profit, this is evident when they stopped bringing back Poro King and Hexakill. Although Howling Abyss has a significantly higher player base than Twisted Treeline they might even go out of their way to only forward the game to Summoner's Rift. This is just a theory so don't hate.