If Office really bogs down, people/organizations will stop buying Office, or will stick with 2010 past MS' planned EOL, and give Redmond the finger. And Microsoft will be forced to dig under the hood for optimizations they'd not otherwise have done.
This is basically what happened with Vista. MS got so much pushback for it that Windows 7 was basically Vista optimized.
I use ancient Sun and DOS machines in the factory installed right next to "upgraded" tools with Windows 7. The Windows machines are slower and the operators prefer the 90's era machines.
The problem is that back in the ancient days they spent a lot of effort on specialization and operability. They had to sell that it was better than the old days. Today it's much more about 'universal' and 'standardization', and they've lost a lot of the operability. They also haven't put enough effort into optimization, especially of the user interface. Or accepted that an interface that requires a bit more training can be far more usable in the end.
