An old thread confirmed that it is not possible to upgrade an FWSM failover pair to a new minor/major version without downtime. see https://supportforums.cisco.com/message/3019703#3019703
What abaut newer versions? I like to upgrade from 4.0(6) to 4.1(2).
With theese versions, is it possible to upgrade without donwtime?
Has anybody already tried it?