Chrome's current extension update model isn't well-suited to addressing problems like this. First, updates don't happen very often - in my experience, once or twice a day at most. So even if a malicious extension is caught quickly, users will likely remain exposed for as long as 48 hours.
If an extension is pulled from the store (DMCA or otherwise), presently Chrome does not warn you or remove it, it just quietly stops getting updates. If Google starts doing remote disable/remove for extensions, there would be some angst over this and the question of when it will get used (court orders from a foreign country? etc.)
