Will Keane (the forward now on loan at Sheffield Wednesday) has never switched association. He has only ever played for England at under-age level, so he can still switch to the FAI if he wishes.
Michael (the defender who has signed for Burnley), on the other hand, represented us competitively at under-17 level first and then represented England competitively at under-age level, thus formally effecting his solitary switch, so he's now tied to the FA.