RIM mentioned that a new game engine is now available for the PlayBook. It is called ShiVa and is actually built on the Marmalade SDK for mobile ports. Their Mobile Application suite now works on the PlayBook due to the Marmalade port. A future update will soon have the ability to directly port to the PlayBook but for now it is supposedly still possible just not as easily through Marmalade.
Read up on ShiVa 3D at this link. They even announced a massively multiplayer game Earth and Legend coming for the PlayBook through this 3D game engine.