As buildd admin I can't directly do the upgrade apart from asking DSA to go ahead this which I'll do as soon as wheezy buildds are figured out for wheezy infrastructure (which is currently being worked on).
Please ask them to use kfreebsd-9 kernel,
as only it have (backported):
* fix_VOP_VPTOCNP_bypass_for_nullfs.diff: Fix /proc/self/exe in
nullfs. (Closes: #682291, #681594)
Petr