There is a ticket for updating Spark to the latest Smack version SPARK-1567 Actually it started with 3.4.0 and then i have modified it a few times. Smack updates are slow in Spark..
4.0.0 is in RC state, so maybe we should wait a little for it to get a final status. Though we can update and test nightly builds and revert if something brakes (in 3.4.0 there were changes to Workgroups, so maybe it affects Fastpath). 4.0.0 contains security fixes and other improvements.
Changes to Smack API: http://community.igniterealtime.org/docs/DOC-2703