For 2016, I'd say the absolute Republican ceiling for the Hispanic vote is probably right around 40%, which would necessitate the combination of a weak Democratic nominee, poor economy, and Republican ticket that makes a very determined outreach to this demographic. A Latino running mate might help, but I don't see Hispanics as being a group that votes strictly on ethnicity. The running mate would have to be personable, moderate, and/or support some form of immigration reform. Susana Martinez and Marco Rubio quickly come to mind, as eric82oslo mentioned. The chances of Republicans reaching this ceiling that I have set would be low, but conceivable, especially if the party is having a really good night.
It's more likely that the percentage of the Hispanic vote that goes Republican if the party wins the White House in 2016 will be somewhere in the thirties. If the GOP loses in 2016, I'm thinking that the numbers with Hispanics would be somewhere in the upper twenties to lower thirties (since the Democrat's numbers with whites could very well improve, especially if that Democrat is Hillary Clinton).
It's hard to estimate how low the floor would be for a fully Tea Party ticket or one that is hostile to the interests of Hispanics.
I stopped reading after 40%. How absurd. Not even close to what they've gotten over the past 8 years.