Earlier today an analyst published a claim that Google would be making Chrome for iOS (iPhone and iPad) and would market it extensively, and basically bring the desktop browser wars to mobile. He didn't claim any sources to go with, anonymous or otherwise, or any leaked information.
If you've ever noticed how much slower web pages seem to render inside an iOS app, that's the reason.
Would Google want to put the Chrome brand on a much slower, thinner web client on iOS? Even if they skin it to look more like Chrome (and UI has always been one of the worst aspects of Chrome), it would always be slower than Safari.
Sure, there are "alternative" web browsers in the App Store, and some people love the extra features they provide, but none of those extra features are better local performance. (And I'd argue proxy performance is minimal at best, and always a trade off.)
Apple takes control and security extremely seriously in iOS. I doubt they'll let third party browser or rendering engines onto the iPhone or iPad in iOS 6 or any time in the near or distant future. Google takes Chrome's reputation for speed just as seriously. I doubt they'll put a frustratingly slow web browser on iOS any time in the near or distant future.
Google could very well be playing around with Chrome on iOS in the labs, but there's nothing to indicate it's coming, at least not based on the information presented to date.
Update: Google announced Chrome for iOS at I. Even with all of Apple's restrictions in place, it seems Google is willing to take that in trade for presenting their interface and, more importantly, their cloud sync services.