People who work on browsers and libraries for them are in a position to make this happen if they want-- to make the Web win as the platform even if the iPad wins as the device. All you have to do is make other browsers fabulously powerful for web apps. If there start to be a lot of things you can do on e.g. Chrome that you can't do on Safari, Safari will be pushed to follow suit.
In fact maybe it will be Chrome and not Android that saves us from Apple's locked-down future. It's certainly a more straightforward problem. Android can only win through partnerships with handset makers, while Chrome can evolve at its own rate.