XML for wireless

I was just wondering if XML is what most wireless companies are using now to organize their content once it is accessed by WAP enabled devices. I mean, can I use XMl to rearrange things for WML and then serve it to a WAP device.

I am trying to learn more about the wireless world of programming and am worried that WML is going to become outdated and have no idea where to start studying things like compression standards and what the latest WAP language is to stay on top of the game, but I am assuming XML is going to be playing a key role.

If anyone knows where their are good tutorials on all of these technologies I am open to them, I am very aware of the ones on Devshed and am using them extensively.

Thanks,

Sean