There are a lot of meta TM and applications globally - e.g.
this search shows 6650. While some are recent, the majority are years old.
Given that meta is also a dictionary word (although I think only since the 1980's), and is part of the name of many existing businesses and organizations (about
6300 active listings according to OpenCorporates).
It would seem an incredible job, even for someone with as deep pockets as FB/Meta, to acquire all existing TM rights. Some seem to have nothing to do with what FB plans for Meta, so my guess is they will be strategic in seeking businesses operating on the name that would overlap with their long term plan. I have no inside information, but suspect priority in trying to seize names would be those in similar category, and those that seemed registered arguably in bad faith.
On the other hand, as
@nametrekker pointed out above, their TM application is way longer than any I have ever read and seems to want to lay claim to essentially any use. What will be awarded though, will be interesting. I suspect many existing companies will file objections.
Bob