"The next generation Sega Saturn was released in 1995 outside of Japan. However its impractical dual-CPU architecture could be seen as a metaphor for the lack of collaboration between Sega of America and Sega of Japan, which led to Sony creating the PlayStation alone rather than jointly with Sega."
There really wasn't any collaboration between Sony and Sega after Nintendo left Sony at the altar. I know that SGI was consulted on Sega's end, but they decided to eventually go it alone (SGI eventually partnered with Nintendo on the N64).
Its also important to remember that the Genesis was a flop in Japan; it lost outright to both the SNES and PC Engine. Sega's big business in Japan was it's Arcade market, so they wanted to build a console that was built on it's Arcade architecture that titles could be ported to easily. By contrast, Sega of America had a smash hit with the Genesis, and wanted to leverage it's install base (hence the Sega-CD, 32x, and Neptune project). These two factions were *never* going to agree on anything. Hence the failure to come up with a successor to the Genesis.