Engaging in some lightly supported speculation, Jason Kottke imagines a browser kitted out and branded by Google. Basically, they'd be stepping somewhat into Netscape's (cement?) shoes, but at least they have a bit of an enterprise background to give them cred, and some other business to fall back on. And if Google stayed away from calling it a product, IT managers could secretly adopt it as an alternative standard. Besides, a little browser competition is definitely Not Evil (TM).
Kottke even hypothesizes a browser based application suite. Not one consisting of the typical desktop suspects, but a Web-centric set including, search, e-mail, blogging, and IM. This is a bit heavier than my vision of each user tricking out their browser with smaller extensions, but the two are not incompatible. Even better, major advancements could be made if Google showed how to integrate every aspect of a the browser UI with serious global scale computing.
Actually, instead of an official endorsement, working on Mozilla/Firefox hacks wouldn't be a bad way for a few Google engineers to spend their hacking time.