Perhaps never?
NoA has shown very little interest in bringing the game to the U.S. EarthBound has not even been put on virtual console yet so its hard telling at this point.
Mother 3 is a role playing game by Nintendo, HAL Laboratory, and Brownie Brown for the Game Boy Advance. It was released in 2006, but it was released only in Japan.
The Unwelcome Mother - 1916 was released on: USA: 3 September 1916
Mother of Pearl - 1915 was released on: USA: 3 April 1915
Billie's Mother - 1916 was released on: USA: 3 July 1916
Crescendo - 2003 Mother's Day 2005 3-11 was released on: USA: 3 May 2005
Cybill - 1995 Mother's Day 3-25 was released on: USA: 12 May 1997
Taxi - 1978 Louie's Mother 3-14 was released on: USA: 26 March 1981
Mother Up - 2013 The Double D's 1-3 was released on: USA: 2013
Disappeared - 2009 A Mother's Mission 3-11 was released on: USA: 14 March 2011
Duet - 1987 His Mother Myself 3-7 was released on: USA: 18 December 1988
In the House - 1995 Mother of Invention 3-2 was released on: USA: 2 September 1996
I Led 3 Lives - 1953 The Mother in Law - 3.18 was released on: USA: 1956