I find it fascinating that Google is always hurting their own mobile experience. Between all the issues android has with wake locks and memory leaks and the massive infrastructure of location and 'lifestyle' tracking for ad delivery, its a miracle Android devices get any battery life at all. Even without this html5 conversion, Android battery life often pales compared to iOS or Windows Phone.
The more I think about it, an OS from whats essentially an ad delivery company is probably a liability. Monetization will trump user experience. Get ready for some pretty invasive html5 ads.