AFAIK some of the other chromium forks (brave and/or edge?) were committed to backporting manifest v2 (or more specifically the webRequestBlocking API) for future chromium versions.
as of yet, there's no (publicly stated) contingency plan if the upstream mv2 code is excised, but I could be mistaken.
all of that being said, I was answering the question about mv2 broadly, not ad blocking.