The SMC Pentax-DA 90mm Macro lens is the World's only medium format lens with image stabilisation built in. It is also an AW All Weather lens, and balance quite well on the large 645D body.
Pentax HD DFA645 MACRO 90mm F2.8 ED AW SR Hands-On Photos of Equipment
Pentax also showed a future roadmap with the following 645D lenses:
- Wide zoom
- Tele Zoom
- Standard Zoom
These lenses are penned in for "2013 or Later" expanding the already quite entensive lens range available.