Guys, Nissan had the RB series engine lifespan planned from the very beginning... they were always going to have the total R+D lifespan pegged at 20 - 25 years. Nissan didn't just suddenly say "geez we're in the sh*t financially after 40 years of building straight 6's, lets build V6's from now on", rather it's a technological, packaging AND financial move. The RB series engines were the best straight 6's in Japan and no other manufacturers really tried to compete at the same level as Nissan.... but where were they gonna go from there?
During the Bubble economy years in Japan, there was serious talk that Japan was going to 'take over the world' financially, so the vibe within Nissan, Japans flagship car manufacturer, was very much a reflection of that: 'let's build the best racing straight 6 in the world and call it the RB26DETT'. So they did. Why the RB26 wasn't changed much over 10 years is pretty much testimony to how good the original design was.
But that was then, now is now, so goodbye RB26...