Digitalcameraworld spotted the lens at the SWPP show in London. They write:
From its size and 77mm front filter thread, it look almost certainly to be a 70-200mm f/2.8. You can also clearly see that the closest focusing distance of the lens is 0.92m (3.02 ft).
It’s likely Panasonic will announce the full specs within the next 1-2 weeks. Fingers crossed the lens has indeed an f/2.8 aperture. While the other zoom lens the 24-105mm lens will definitely be a f/4.0.