You can bet 300 new uBlock replacements to spring up practically overnight, some of them scams, reducing trust in the Google ecostystem.

Unfortunately it's a bigger problem.

Google doesn't plan to block uBlock Origin itself, but the APIs it uses to integrate into Chrome in order to function. This will effectively disable all adblockers on Chrome. uBlock won't be removed from the Chrome extension store, it will just have 90% of its functionality removed.

Additionally, this isn't a Chrome-only change, but a change in the open source Chromium, an upstream browser of Chrome all other Chrome-based browsers use (essentially everything aside from Firefox and Safari themselves).

The change itself is involved in changing the browser's "Manifest", a list of allowed API calls for extensions. The current one is called Manifest v2 and the new one was dubbed Manifest v3.

Theorethically Chromium-based browsers could "backport" Manifest v2 due to the open source nature of Chromium. However that is unlikely as it's projected to take a lot of resources to change, due mostly to security implications of the change.

Vendors of other Chromium-based browsers themselves have little to gain from making the change aside from name recognition for "allowing uBlock", which most users either wouldn't care for or already use Firefox, so the loss for Google isn't projected to be large, just as the gains for other vendors.

TLDR: uBlock won't be removed from the Chrome extension store, but the mechanisms through which it blocks ads will be blocked. The block isn't a change in Chrome but in Chromium and affects all Chromium-based brosers (all except Firefox and Safari). Other vendors could change that to allow adblockers but it's projected to take a lot of time and resources.