Hi, Thunderbird 3.1.10 in Mga 1 has some vulnerabilities and should be updated. http://www.mozilla.org/security/known-vulnerabilities/thunderbird31.html
Unlike Firefox 4, the Thunderbird 3.1.* branch seems still maintained by mozilla; 3.1.12 is planned for 16/08/2011 https://wiki.mozilla.org/Releases/Thunderbird_3.1.12 .
So we can stay with the 3.1.* branch, and update Thunderbird to 3.1.11 (the version that we have in cauldron since 21/06), or try to update to the last version 5.0 (we have a request for Thunderbird 5 in bugzilla https://bugs.mageia.org/show_bug.cgi?id=2088).
Personnaly, I would prefer that we stay for now with 3.1.11 (and probably 3.1.12) in Mga 1, and that we update to Thunderbird 5 only in cauldron, and test it for some weeks.
WDYT? -- Luc Menut