I have used they when speaking publicly about actual person while trying to protect the person's identity. I try not to speak directly about my family and friends online.
Until someone comes up with gender-neutral personal pronouns, it's required. Some ppl just aren't binary - never mind XXY, there's also the entire trans community and some folks who just don't have a sexual identity of any kind. The person who i used to refer to as my niece and is now my sister's nonbinary child is quite definitely a "they" - asexual.
Grammarically, I'm inclined to say he/she because of the singular/plural issue, but I absolutely accept that some people are non-binary and refer to themselves as 'they', so I believe we should accept them/they and move on.
The answer to the question is "no"; however it will happen anyway because so many people think it's a good idea. The reason for the 'no' is because these "many people" don't know that there already exists perfectly useful non-gender specific, singular, third person pronouns such as "one", "someone", "anyone", "oneself", "who", "whoever", etc.
Slartibartfast 