Nikon, Canon, Pentax and Minolta are not using the 4/3 system as they have a huge 35mm base already. Hence they will prefer to stick to the 35mm standard. Only Fujifilm, Kodak and Olympus is doing so.
BTW, incorporating image stabilization in the body has been done by the Dynax 7D from Minolta. Lens stabilisation is done by Canon and Nikon. Each has its own benefits. But I personally prefer Minolta's method.
And for those who are asking if a DSLR from Panasonic is a big deal... YES it is! There is a whole system required to backup the DSLR or any film SLR system. That includes lenses, accessories, flashes, software, etc, etc..... it's very complicated and requires rather specialized know-how... I presume Panasonic will tap Leica's experience although Leica caters mainly to the top range consumers... Not easy to break the stranglehold of the 4 top brands....
I suspect Panasonic might go the way Fujifilm did.... borrow the F-80 body to produce the S2/S3Pro.