What is the development platform for Windows Phone 7

Question

If I want to develop for Windows Phone 7, what should I learn? XNA, Silverlight or other?

Answer 1

Microsoft has not yet announced what the development environment will be. They say they'll get more in-depth at MIX. If I were a betting man, I'd guess you'll get XNA out of the box, followed by some light version of Silverlight.

EDIT

I'd say it's no longer a guess that it will be Silverlight and XNA just based on the MIX sessions for Windows Phone.