If that's the "downloadable RS" they talked about in the QA, I'm disappointed. It's still the same old Internet Explorer based browser. IE doesn't even support the resizable mode of RS, so why does Jagex make it IE based?.

Jagex make everything based for Firefox as they use it on all their computers.

Well yeah, of course a Windows only product is going to require IE, the game itself and all their web-links are such are tested primarily in Firefox.

 

I'm not sure about the new client they have planned though, I heard that it's going to be built in Java similar to how Metis was/is.

This was die for a lon time. The current client is nothing but a compiled link to their webpage run through IE. Hopefully, they'll include extra features (maybe IRC links, Grand Exchange database integration, etc).