I reseached and engaged the BU on this and the main feedback is that there is currently no roadmap for Jabber for BlackBerry PlayBook .
You can check out BlackBerry MVS which is a partner solution from RIM that integrates directly with Unified Communications Manager via SIP. This solution provides natively integrated voice over WLAN/mobile data as well as cellular voice (dual-mode). In addition it provides single number reach and dial-via-office. Unified CM provides device registration and call routing for the solution. You can find more information about that solution here: here: http://www.blackberry.com/mvs.
What about converting the Android Cisco Jabber APK to run on the Playbook? That seems like a logical approach to cover this platform. Has anyone tried it out? I would be willing to convert the APK files and do some testing.