Zeiss 100/2 Makro Planar is definitely next - I've been using my wife's Canon 100/2.8L IS Macro too much, and I have a soft spot for the Z100M.

After that, probably the new-model 100-400, the new-model 24-70/2.8 (shifting my existing one to remote duty), and the 16-35/4IS (then definitely selling our EF-S 10-22, and possibly selling our 16-35/2.8II or at least shifting it to remote duty).