Hispanics are not the reason Republicans lost in 2012. Mitt Romney could have gotten 70% of the Hispanic vote and still lost. Republicans would be better served by improving their numbers with blacks instead.
Good luck on that, considering the Southern white portion of the Republican base, and the ingrained negative attitude African-Americans have towards the GOP at this point.
Any immigration reform that passes a Republican House will be enforcement first, legalization later, and citizenship only when the federal government can prove to congressional Republicans that they intend to enforce the law as written, the border with Mexico is secure, and we have effective systems in place to identify and prosecute visa overstays and ensure that the hiring of illegal immigrants is prohibited as much as is practically possible. Republicans already think that what Democrats want out of immigration reform is new Democratic voters to create a new permanent majority, so they will be very skeptical of anything Democrats put forward on this issue.
You must also factor in that migration from Hispanic countries is a net zero right now and that the growth in Hispanic population is from Hispanics who are already here. With each successive generation of removal from immigrant ancestors, Hispanics become less Democratic (immigrants are the most Democratic, 2nd-generation are less Democratic than immigrants, 3rd-generation less Democratic than 2nd-generation, etc.), so you'd expect that they would become more Republican over time unless Republicans further alienate them.
Here's the thing: what exactly could the Republicans do to embrace issues that African-Americans (and other voters, but especially them) care about? How exactly can they outflank the Democrats on those issues?
As for your last sentence, the "unless Republicans further alienate them" is key.
Also, just as traditionally Democratic ethnic minorities are becoming slightly more Republican, traditionally Republican ethnic minorities (the anti-communist types, like Cubans, Vietnamese, Korean, etc) are also becoming more Democratic. I mean heck, look at what happened to the Muslim-American population. In one fell swoop the Republicans lost that vote (which is rising whether or not the whole Syrian refugee thing shakes out) for a long, long time. And it used to be a Republican vote!
I'm not saying "DEMOGRAPHICS" will ensure a majority for Democrats, but the Republicans have a lot of work to do.
