I've been concerned about this as well but I read this in another thread, it makes reference to the new Panasonic consumer models in Japan.
"The new VIERA TH-PX300 plasmas are available in three screen sizes (50-inch diagonal screen measurement, 42-inch and 37-inch), all featuring the new PEAKS (Picture Enhancement Accelerator with Kinetic System) processor that enables rendering of 3.62 billion colors. This technology is unrivaled in the world providing 2,048 steps of gradation to deliver greater image depth. The current high-end VIERA models offer 1.07 billion colors and 1,536 steps of gradation. Panasonic's proprietary PEAKS technology has elevated the flat-panel picture quality to new standards."
What I take from this is that even though it mentions the new generation glass can support 3.62 billion colors with 2,048 shades of grey it implies that these specs are achieved via Panasonic's own PEAKS technology and are not necessarily present otherwise. This would explain why the new Panasonic Onyx displays have the 1.07 billion colors and 1536 shades of grey specs, suggesting they do not use the PEAKS technology.
Until I hear otherwise I would tend to agree with Steve that the new specs we are seeing are a result of on board video processing and not inherent in the panel on it's own.
Rod