[quote=@Volenvradica]

So, why is there going to be a Sword Art Online movie?  
[/quote]

So that they can milk to cow dry, if there's money to be made you can guarantee someone will want to capitalise on it.  Plus ClockTowerEcho's point.

Then there's also the same reason there's a Deadpool movie.  It becomes common knowledge then the fanboys/girls whine at the producers to ensure that it happens.