Metro Web Browsers on ARM

We know that Firefox and Chrome are both coming out with Metro style browsers for Windows 8, and they're using a special exception to the rules that lets them bundle the Metro UI in with their regular desktop apps. That sounds great for x86 PCs, but with ARM tablets not being able to install third party desktop software at all, are those users going to be stuck with IE10 exclusively? Or will there also be an exception to the ARM desktop rules for web browsers?