Regardless of count of native and non-native speakers, singular they is still 800+ years old in English. It is ambiguous without context around the potential count and it's unlikely the conjugation rules will change in the next few years to accommodate this. However, in English (and I suspect most languages) it's generally not common (or it is discouraged) to drop in a pronoun without sufficient context to identify the individual or group that it describes, which also includes count. So even if the verb conjugation remains ambiguous (with a phrase or sentence taken out of context), in context it should make sense so long as the person is semi-competent in communicating.

"They need access" - no context, ambiguous.

"They need access" while pointing towards an individual, unambiguous; while pointing toward a group of new students on the first day of school, unambiguous.

"They need access" in an email as a single line or a subject with no message body, completely ambiguous and will elicit a response of "Who needs access?" If it's part of a prior conversation chain that the recipient can recall, they'll give access to however many individuals they are aware of be it one or one hundred because it's unambiguous in the context (for them, but not for us).

Perhaps worth mentioning that "you" is "ambiguous" in exactly the same way: it's grammatically and historically plural but can now refer to either a single person or a group.

French and German also use a grammatically/historically plural form for polite "you". But Italian seems to use a feminine third-person pronoun for that purpose ...

You is historically plural?

I knew it could be applied to a group in certain cases, but only when referring the group as a single unit, really still singular. Or when speaking one-to-many, where each recipient is meant to hear you to refer to themselves, though the speaker spoke to a group.

"you 12 come with me" is really still referring to a single unit to me, the group, not the individuals. IE, it conveys no more meaning than saying "you come with me" where the object might be either a person or a group equally.

It's interesting, I don't think English has a way to distinguish "me singular" vs "me a member of a plural", other than by adding other words like "you all"

That is a pretty interesting idea. I love the idea that someone starting out with the desire to project their will on the rest of the world, becomes so successfull that they no longer own their own language. "If you didn't want other people to mess up your language, maybe you shouldn't have insisted that everyone else speak it?"