This is pointless, kernel will be updated via freebsd-update only if it have security bugs, in your special case, problem is in BIND - not in kernel - reason why output of
uname -a is still same.
From:
http://security.freebsd.org/advisori...08:06.bind.asc kernel is not mentioned.
Conclusion,
uname -a doesnt need to get changed after every update.