It definitely doesn't make a lot of sense for several reasons if you understand Riot. I am not saying it won't happen but it would require Riot compromising on a lot of important issues.
Riot has to control access to the game, and with all the work they have done internally with player attitudes.
Riot makes money hand-over-fist with a free to play game. Would it be on the Xbox shop? Would you need Xbox Live gold? How would MS take their cut?
RTS just doesn't play well on a controller.
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