It's all in how patient you are. I'm using a 2.5 year old MacBook Pro and LR4 and CS6 and it takes longer to work on a D800 file than it did with my D700 but not enough for me to upgrade the mac. I did end up getting an SSD, though, and it did help. So for much less money I got a nice performance boost.
And I think that even updating lenses for the D800 is generally overstated for anyone who displays on the web or prints less than 24x16.