No, they made it possible to port XNA games to the platform. Except that XNA != XBOX SDK.
XNA is a .NET-based game SDK that some people have used for Xbox Arcade games. As far as I know it hasn't been used for any disc-based games. Games like Modern Warfare are written in C++, top to bottom, with potentially some Lua for scripting.
Lack of C++ is a huge issue on WP7, ask any game developer you know who is working on the platform.
XNA is a .NET-based game SDK that some people have used for Xbox Arcade games. As far as I know it hasn't been used for any disc-based games. Games like Modern Warfare are written in C++, top to bottom, with potentially some Lua for scripting.
Lack of C++ is a huge issue on WP7, ask any game developer you know who is working on the platform.