I’ve been using “guys” as gender-neutral for 45+ years, so obviously the same with “you guys.”
But “y’all” is an even better second-person plural, IMHO, and I use that a lot more often than “you guys.”
Those of us who grew up watching The Electric Company know that “Hey, you guys!” is genderless.
Huh. I think you guys is completely gender neutral and will happily address groups of women that way, either verbally or via email. However, I really dislike “mankind” and never, ever use that word, because it doesn’t read as gender neutral to me.
I never hear that, but I do hear men, including straight men, affectionately call a group of men they’re talking with “bitches.” “All right, bitches, let’s play!” that kind of thing. And I don’t know what to think about that.
I use “guys” in a gender-neutral way, including referring to groups of girl students as “guys.”
I don’t mind “you guys” applied to a group of all women, or to a mixed group (I’m female, by the way). I say “you guys” to my female friends and nobody seems alarmed.
I always thought English was a weird language for not having a universally accepted you-plural form, a “vous” or “ustedes”. That why while I’m not fond of the southern accent and dislike some of the regional jargon I hear around here, I’m a big fan of “y’all” now.
I would also like it if “ladies” was the default you-plural. To the women, it seems classy and complementary. If addressed to a group of men, the speaker sounds like a drill sergeant or a football coach.
Gender neutral. And I use it all the time. I also a Chicagoan - if I used “y’all” I’d sound like a freakin idiot. 
“You guys” is genderless. As is “those guys”, “these guys”, “our guys”, “your guys”, “youse guys”, “dem guys”, “Fred’s guys”, and “my guys”.
I say gender neutral, but as I said in a previous thread on the same topic, it’s not unanimous.
Gender neutral in the present day and outside the South. But in the 1990s I heard a bunch of women from Houston complain how coarse and offensive they thought it was when they were referred to as “you guys.”
“Y’all” is nice but it does take a bit of practice for a northerner like myself to incorporate it into everyday speech without feeling self-conscious. I think I’ve done it, though.
The english language would be greatly improved bt the adoption of the northern england 2nd person plural “yous” .
As well as being useful addressing groups it is also very useful when arguing with the representative of an organisation. “Yous” will clarify that it is the organisation, not the individual, that you are criticising.
I think I use more often than not “folks” as a 2nd person gender neutral plural.
I find that even “guy” is mostly gender neutral, with a slight preference towards male.
And you gals isn’t usable mostly because “gals” itself is kinda hard to use, and “gal” is mostly used as a joke.
And I prefer “humanity” to “mankind,” though I can use “humankind” for effect.
Shoulda known a previous thread would exist-- seems like everything’s been asked here. It was interesting reading the responses in the 2006 thread vs. this one-- seems like it was mostly leaning toward ‘guys’ being gender-neutral then, but perhaps has gone a little bit further toward being universally gender-neutral in the 9 years since, judging by the responses here (for which I thank you guys). I know, too small of a sample size, but it seems like the overall opinion is a bit different.
So, unless English comes up with an “official” gender-neutral group pronoun that is non-regional (being a lifelong northerner, I can’t really pull off y’all), I guess ‘guys’ it will be.
Fun fact: the “y’all” contraction is, completely independently, found in South African Indian dialects as well. But not, generally speaking, “All y’all”
South African English has a “Yous” as well (pronounced with a short -u- sound like in push, not a longer -u- like in Jews, not sure what the NE pronunciation is) but it’s considered infra dig - it mostly shows up in heavily Afrikaans-influenced dialects like Cape Flats English. It is very, very useful, though.
I’ve taken to actually saying “You Plural” when it’s not clear from context…
Really, it’s more that we’re missing the you-singular, “thee” and “thou” having fallen from use in standard English some centuries ago.