The absence of a plural form of 'you' is one of the
Great Failings of Modern English. Even worse, given the past usage of 'ye', 'thou and 'thee', it seems English has actually gone backwards over time. Modern 'you' has lost the ability to differentiate between singular and plural or formal from informal. Like other versions of English, Australian English got around the 'you-plural' problem by informally inventing its own versions - 'yous & 'yez' - typically in Australian bogan speech. (a 'bogan' is a 'yobbo'

)
As an etymological amateur I have long been aware of the (mainly) Southern US solution to you-plurality by using 'you-all' or its cousin 'y'all' in informal usage.
However... as an ardent listener to spoken English (in this case American TV and movie speech) I suspect that 'y'all'/'you all' is', in some US dialects, losing its unique status as a plural form of 'you' and is actually replacing singular 'you'.
As it turns out a couple of Dictionaries also agree with me:
The world's leading online dictionary: English definitions, synonyms, word origins, example sentences, word games, and more. A trusted authority for 25+ years!
www.dictionary.com
There is significant debate about whether y’all can ever be strictly singular (without implying a larger group, association, or network). Such examples are uncommon and judged as ungrammatical by many speakers who otherwise freely use y’all themselves. In the rare instance of singular y’all, it is best understood as a pragmatic choice to communicate friendly solidarity, or to express group membership as a speaker of Southern American English.
you —usually used in addressing two or more persons… See the full definition
www.merriam-webster.com
: YOU —usually used in addressing two or more person
What appears to be happening is the wholesale replacement of 'you' by 'y'all' in informal (Southern US) speech. This means that 'y'all' is becoming
both the singular
and plural version of 'you'.
OB