I think it is a bug that the 2.0 sources are only in buzz/binary-i386/devel, and not in buzz/binary-all/devel. Moreover, they are neither in unstable or in rex.
Here's the output from a find on master: $ find . -name kernel-source\*deb ./unstable/binary-alpha/devel/kernel-source-1.99.7-0.deb ./unstable/binary-i386/devel/kernel-source-1.99.7-0.deb ./unstable/binary-m68k/devel/kernel-source-1.99.7-0.deb ./unstable/binary-sparc/devel/kernel-source-1.99.7-0.deb ./unstable/binary-all/devel/kernel-source-1.99.7-0.deb ./buzz/binary-i386/devel/kernel-source-2.0.0-0.deb <----- the only one ./buzz/binary-all/devel/kernel-source-1.99.7-0.deb ./rex/binary-alpha/devel/kernel-source-1.99.7-0.deb ./rex/binary-i386/devel/kernel-source-1.99.7-0.deb ./rex/binary-m68k/devel/kernel-source-1.99.7-0.deb ./rex/binary/devel/kernel-source-1.99.7-0.deb ./rex/binary-sparc/devel/kernel-source-1.99.7-0.deb -- Dirk Eddelb"uttel http://qed.econ.queensu.ca/~edd