As a old Sigma cams user, i can tell you that if this rumor is real you can only expect...
Newest Foveon sensor it's a terrible mistake, there is almost half a year after Quattro introduction and Sigma can't get noise level right even at base ISO100, just look at pictures there is so distinctive noise in blues and light parts of the images that even older sensors not only Merrill but even 1.7 crop Foveon sensors can get better results.
This is all very amusing to me. When Sigma Foveon cameras first hit the market, users were literally RAVING about them. They were putting down Bayer sensors in the market, especially the CMOS sensors from Canon. Of course, all problems associated with Foven sensors were either disputed, denied or dismissed.
Now, the skeletons are coming out of the closet. I am wondering if this may also be true for current users of other competing brands... you know who you are.
Anyway, like what I said earlier, if this mutlilayer sensor technology indeed comes to pass, we can be sure most of the apparent drawbacks will have been ironed out already. Didn't folks make the same dire prognostications when Canon first announced their implementation of CMOS instead of CCD sensors? Sigma may not be able to resolve the accompanying issues of multilayer sensors, but this does not imply Canon and Sony (which also has patents on multilayer sensors) do not have other clever tricks up their sleeves.