Well here is the trend...
00 04 08 12
Black 9 11 4 6
Latino 35 44 31 27
Asian 41 43 35 26
My guess for 2016
Black 8
Latino 33*
Asian 33*
Which means the GOP will need 61%+ of the white vote to win
* A LOT depends on the GOP position on immigration. Polling has shown that support for a path to citizenship makes a big difference (and Bush's 2004 seems to back that up). I am assuming that the GOP nominee will not back a path to citizenship.
It depends on the candidate
Bush Rubio Walker Paul Cruz Christie Trump Huckabee
Latino 42 37 26 30 24 35 19 31
Black 9 7 6 9 4 6 1 6
Asian 38 33 22 26 19 26 26 24