OJ Mayo is currently shooting 52% from 3 point land. His career average is around 36%. He is NOT going to be able to keep this up. That is a completely unsustainable jump ... I don't think you could find any player in the history of the league who has jumped almost 20 percentage points in shooting efficiency in one season. Not going to happen.
His FGA per game have not increased noticeably (19 to 20). He is just on a hot stretch.
Not that he is a bad player, by any means, but the way he is playing now is not how he is going to play all season, unless we are witnessing literally a once-in-the-history-of-basketball Most Improved Player campaign.