From the cairo list, so don't assume it's the official word, but it sounds plausible:
My understanding of the MS plan is that DirectX is going to be their new base driver layer and GDI/GDI+ will be phased out over time. The drawing API will be the dotNet Avalon one. Of course this is going to take years to happen. Avalon is similar to Cairo and can print.Speaking of which, there was a talk from the SETI@Home guy today about distributed computing and to promote his new system/platform for this sort of thing. Three noteworthy bits were: the graph showing the relative sizes of your computing power, the computing power of all businesses combined, and then the huge overwhelming power of all homeowners combined; the observation that consumer-grade hardware will always surpass specialized hardware in terms of price-performance due to economic reasons, with GPUs as an example of that; and also that they have a half-million CPUs in their "supercomputer".
The shift from a GDI base to DirectX is parallel to the shift from X's XAA to X on GL. Basing things on DirectX/GL allows access to more hardware accelerated drawing functions, especially alpha blending.
DirectX 10 has spec'd hardware changes to accelerate drawing of alpha blended text with subpixel positioning and to increase the speed of drawing context switches.