According to a trusted source the GH3 will support the just announced new AVCHD 2.0 codec with 1080p60/50 and maximum bitrate of 28 Mbit/s. As you know the current GH2 uses a native 60p sensor but file gets stored in 24i or 30i only (50i at 720 lines). Below you can read the specs of the new AVCHD 2.0:
Links to the current GH2 at [shopcountry 16254].
Links to the first GH1 camera at [shopcountry 14826].