Amy Walter has a piece on 2016 demographics and what Republicans need to win in order to win the Presidency. She cites Whit Ayers saying that the electorate will be 69% white and 31% non-white. Since Ayers is a Republican pollster, she believes that makes a claim of such a non-white electorate credible. Ayers, last seen steering John Huntsman into an iceberg, and the other Republican pollsters do have an agenda. They want to win and doing better with minorities is definitely a way to do that. So they proclaim Republicans are doomed if they don't panic and win more minorities. If you say doomed people will listen.
The reality is somewhat different. The electorate in 2012 was 73.7% white and the electorate has been getting roughly 2% less white with each Presidential election. If that continues the electorate would 71.5% white. That's certainly possible, although it's also possible that minority turnout drops without the first minority President on the ballot. I could see the electorate being more white than 71.5%, but it's unlikely it'll be less white than that. An electorate with that high a minority population certainly is daunting for the GOP.
We should keep in mind, however, that Republican congressional candidates did about 1.5% better than Romney did nationwide. If Romney won Whites 59%-39%, they likely won them by 60.5%-37.5%. Additionally, Democratic support has been eroding with whites in every election, even those that didn't have Barack Obama. The idea that Hillary Clinton will do better with white, college-educated women than Obama isn't supported with any data. She might, but she could certainly do worse.
The states with the largest shares of Hispanics are mostly not in play in 2016. Improving on Romney's shares by 10% among Hispanics still won't win New York, California, Illinois, or New Jersey and it's not necessary to win Texas and Arizona. Yes, doing better among Hispanics could put Florida, Nevada, and Colorado in the GOP column, but Florida has had an R+2 PVi the last two elections. If a Republican candidate is running even with Hillary Clinton nationwide, it's hard to not see Florida already won.
On the other hand, some of the swing states (e.g. Iowa, Wisconsin, New Hampshire, Ohio, Pennsylvania) have small to nonexistent Hispanic populations and three of them have small to nonexistent Black populations. If a Republican could get the White voters in Iowa, Wisconsin, and Minnesota to vote the way White voters did in Missouri or Indiana in 2012, all three could go into the GOP column.
The idea put out there is that Republicans can't win without doing better with minorities. It's not nearly that simple and that might not even be the path to victory.