This is long-term positioning for Google; they are clearly trying to build a more stable application platform for web-based development. All of their changes (security, sandboxing, process isolation) are clearly intended to make the browser a better application for hosting complex apps.
This is what Microsoft was worried about with netscape, and why they broke antitrust rules to "cut off their air supply". It's going to be interesting to see how MS responds.
It's also interesting to see how the mozilla / firefox team deals with this- Google is pretty much funding firefox now, so it's going to be a potential conflict of interest for these folks down the road.
In a nutshell, things are going to get more complex, require more testing, and will (hopefully) force recalcitrant vendors like Microsoft to become more standards-compliant.