Using LGPLv3+ license for libgnutls?

[Simon Josefsson]

RMS asked if there are is reason GnuTLS should remain LGPLv2.1+ instead
of using LGPLv3+.

The reasons I'm familiar with includes lynx under GPLv2-only.  Gnucash
is also said to contain GPLv2-only code.

Are there other reasons not to use LGPLv3+?

I recall hearing about policies that mandate LGPLv2.1+ in some projects,
for example the core libraries in GNOME, but I cannot find any reference
to this out there.  Anyone?

/Simon