Um, no.
<ahem><ahem>[Ahem]
"Y'all" is prescriptively correct, in that the contraction is in this location.
However, assuming you are referring to the vernacular of the Southeastern United States, Ya’ll is pronounced [yawl] <yawl>, as it's the extremely colloquial contraction for "ya will" and the "a" reduces to schwa because we're lazy when we speak. It has traditionally been spelled for this pronunciation, and the better spelling just grates because it ruins the pronunciation. I simply feel that the spelling change is causing pronunciation confusion and essentially leading to people butchering my native vernacular, all for the sake of putting an apostrophe in the traditionally wrong, but technically correct, place.
...Which, imho, is a stupid reason to mess with something. You learn exceptions to the rules all the time in English, and ya'll needs to remain one of those exceptions.
Yes, it is illiterate. It is a word of a person who has gone a summer without shoes, who hangs their (singular, before it was acceptable) warsh, and wears homespun and hand-sewn dresses. That is the point of its existence.
Further, if you do not accept the above, the second best reason of why it’s Ya’ll instead of Y’all is BECAUSE the dictionary spells it Y’all. You can’t let a bunch of Yankees in NYC dictate how to spell it. Consider: insist on the “ya’ll” spelling and enjoy foaming at the mouth from all northerners (i.e. Yankees).
Finally and definitively, “ya’ll” is without question the correct spelling, as that is the way Mark Twain wrote it.</yawl></ahem></ahem>