GnuTLS will soon release 2.4.0. The 4th release candidate 2.3.15 should be available in experimental after the next dinstall run/mirror push. The upgrade and propagation to testing should be smooth, since the soname was not bumped. (The only tricky stuff was moving OpenPGP from gnutls-extra to gnutls, but since usage of gnutls-extra also requires direct linking to gnutls a soname bump could be averted.) Preliminary release notes are here.
Anyway, I would appreciate if you could give 2.3.15-1 a short test. Add experimental to your sources.list and install libgnutls26=2.3.15-1 libgnutls-dev=2.3.15-1.
FWIW I did not find any (new) problems when rebuilding the packages build-depending on libgnutls-dev. Now I only need to doublecheck with -release when an upload to unstable would work for them.