I think it would be more like 6D-2R or 5D-3R. Clearly the SF Bay-based state would be 2D, but L.A.-based would be 2D as well (probably 2 La Raza Moonbats), San Diego-based would be marginal (probably one of each, a liberal rodent and probably a RINO), and Inland Empire/Central Valley would probably have 2 Republicans, but from the flood of liberals leaving L.A. and the SF Bay area, within 20 years, perhaps less, it could be outnumbered, and hence all 8 could be Democrats.
If we split the state in two rather than four, ie, create Northern California and Southern California, would the Senate breakdown be 2D-2R?
I posted a few months ago with info about CA split into 5 states. The SF Bay and LA County states would be ridiculously Democrat, but the three “normal” states (one in San Diego, Orange and Imperial Counties, the second in the Inland Empire, Kern and Ventura Counties, and the third in the Central Valley, Sacramento County and the areas to the north) would have voted fairly comfortably for Bush in 2000 and 2004 but would have voted for Obama in 2008. Impy, you may be able to find the post easier than I could.