Hello,
As a user of both Nuendo and Cubase and experiencing the long save time problem, I tried opening a N6.5 project (90+ minutes, 200 tracks, video…) in Cubase Pro 8. The long save time problem was gone. Even loading time was much shorter.
It definitely looks like SB have found the solution introducing it in C8 first (obviously), and then in the upcoming Nuendo 7.
Let’s take this as good news and keep our fingers crossed.
Good luck to all.