A linguistic prediction:

The word "they" is singular as well as plural. I mean, we're now at the point where we can just plain say that -- not that "some people use 'they' as singular" or "I wish we could use 'they' as singular". We're now basically at the point where someone uses "they" for a person of unspecified gender. It's not yet used as a true generic term -- you STILL use "he" or "she" exclusively when the person is known to have a male or female gender, but I bet even that will go away after a while.

But here's my prediction:

"They-all". Or "theys", but basically "they-all" or "they'll" as short for "they-all" instead of "they will."

"Theys guys" or "them guys" will exist, too, but be more regional. "They-uns" has a low probability, but is still possible.

Still -- five, ten years to "they-all". At the outside. Could be quicker.

See, when we repurpose a plural as a generic, we leave a gap for the plural. And we fill that gap in. Ever since we replaced "thou" with "you", we've needed an actual second person plural, which is why we have "y'all", "youse", "you guys", "youse guys", "y'alls", "all y'all", all the way up to "all y'alls". Although the superplurals are fairly rare. It's mostly "y'all" and "you guys"

Once "they" is fully established as both a singular and a plural, and "he" and "she" start falling away like "thou" did, it will leave a gap for third person plural. And that will be filled with "they-all".

75% probability, as a gut feeling.