Is digital marketing to Hispanic audiences shaping up to be the next big opportunity?

Its not the the Hispanic or any other ethnicity has been left out, or 'suddenly' increased in size that simply cannot be ignored. Niches are everywhere. Vertical niches like targeting Hispanics or any other ethnic group, language, country, etc. is already being done. Maybe not at the scale it is being done in English language to everyone, but it is being done.

To answer your question, if Hispanic marketing is the next gold rush --- No. It is not.