How are they going to do this exactly?
If ad blocking software is working properly, the ads are blocked, how is Facebook getting around it? Are they serving them from facebook.com URLs indistinguishable from the URLs that serve content, so there's no way for the blockers to know what to block? Or are they detecting the presence of ad blocking and refusing to serve you anything unless it is disabled?
It is all irrelevant anyway, as I never visit Facebook on a browser, only on my phone. There's no way to block ads in the mobile app, though fortunately the ads (i.e. sponsored pages) are fairly innocuous. The real problem with ads is when you leave Facebook to visit a site linked from Facebook, and you have to endure the horror of what the web looks like without ad blocking software (since it is using a browser built into the app instead of opening it externally via your phone's app, and their built in browser doesn't support the OS ad blocking or at least it doesn't on iOS)
I imagine Facebook is probably getting a cut of those ads on linked sites, so they ought to be able to drop ads within the site itself entirely. Or I should say they "could" do it, but they won't because they're fucking greedy bastards.