In an interview with AP, Ichiro Kitao (director of Panasonic's digital stills camera business) reveled that Panasonic is working on a very high quality Micro Four Thirds camera:
"I want Panasonic to be known for very high-quality cameras, and we are currently restructuring the range of products that we offer to include a very high-end model, but we do not need to change our sensor size to do so. It already offers enough space for good resolution, and is actually not much smaller than APS-C anyway"
From the interview is clear that Panasonic has no future plans to produce cameras with a sensor larger than MFT.