As the landscape and testing evolves for FLoC and the Privacy Sandbox, so too will the reactions and responses from other parts of the system. Identity Resolution firms are going full speed ahead with high-value targeting options in a post-cookie world, and several top adblocking vendors have stated they plan to block FLoC-based ads.
Brave browser and DuckDuckGo have both announced intentions to block FLoC.  AdGuard tweeted that they are set to block FLoC, users of uBlock Origin are pushing for the same, and even WordPress announced they are treating FLoC as a security concern.