The Track Versions and Track Visibility (now in project page) is definitively worth the price.
If they follow what they did with Cubase, you will pay the same for going N6 > N6.5 > N7, as if you are waiting to go from N6 > N7 in one go (paying in two smaller chunks instead of one larger).
The only difference is maybe a year or more without at least two great features.
Haven’t tried the workspaces yet, but Mixer configurations are working better in N6.5. Let’s see how these works together?