The “browser as a platform” is coming along nicely. The following are a few recent developments.
New browser features. Browsers are getting features that were once reserved for operating systems such as key-value databases (look at the editors of the linked document to see how widespread this standard will become), 3D graphics, and more.
Installable web apps.Chrome has them, as does Firefox. That means we get the option to either quickly test drive a web application or to permanently install it. There will also be a way to pay for web apps (necessary for them to compete with native apps).
Stealth web apps. You might already be running web applications outside a browser without knowing it. For example, this article lists how many iPad applications use HTML5 to display their content. This allowed the developers to quickly port them to the Chrome app store. It also lends further credence to the prediction that one day, most applications will be based on web technologies. For mobile apps, they already are the easiest cross-platform strategy.