Ah, yes. There comes a point in every engine's life where, in order to be hip and cool and eligible to play with all the other cool engines, it must succumb to deferred rendering. XDX is no different.
It will be a long and painful process of converting the existing pipeline to support the deferred renderer, but it will certainly be worth it. During the process, I'm also hoping to unify many of the draw shaders to make everything as simple and clean as possible.