1) Mass combat (detailed and flexible, and not dependent on having lots of minis, but still including the effects of battlefield tactics, as well as the effects of cutting supply lines, etc) - I'm hoping the Malhavoc book meets my requirements; based on the info over at the Malhavoc site forum, it looks promising...
2) Rules for running a kingdom/barony/small realm (including natural resources, taxation, and population "general happiness")
3) More adventures, especially high-level ones (levels 13-20)
4) Loads of Epic Level support (both from WotC and others when the ELHB hits the SRD).