I saw this the other day on the B&H front page.
Hands-On Review of The Ricoh GXR Modular Camera System | Digital Photography insights
I have a GX100 and the only 2 places I could find that carried Ricoh cameras in the US were Adorama and Amazon.
I think the idea is great, not only does it eliminate the dust problem, but it lets you have different sized sensors depending on your needs and lets you up grade your camera body.
There has also been talk of a lens mount unit. I don't know if it is technically possible, but it would be awesome to see it in K-mount.