From no less a source than the Economist:
DISCUSSIONS of Texas often turn to an exploration of the American South’s most distinctive regional locution, “y’all.” The common view, among outsiders, is that insofar as “y’all” is from the region specified, it’s also a bit sub-literate and redneck.
That’s a bit snooty. The fact is that “y’all” is pretty useful, as formal English doesn’t have a distinctly plural version of “you.” There is no “yous” (except in places like New York city and New Jersey, sometimes in the form of “youse guys”). This suggests that the referent is usually clear enough in context. But the existence of “y’all,” the related “you-all” and “all-y’all,” and other workarounds like “you guys” and “you lot” show that there is, in fact, room in the market for new second-person plural pronouns. Visitors to Texas typically realize the value of “y’all” within 48 hours.