Just to throw out one random thought, but you could do what many other architecture firms are doing and go from medium-large to small.  Then it would be easier.

A few individuals either already were or became Revit 'experts' and started by implementing it on one project. Almost every new project is Revit based and has a Revit captain who helps mentor newer Revit users. We also have Revit standards and templates much the same as we do for CAD. As it becomes more common people will pick it up. If there are no or few people with Revit experience consider a Revit training course for some of your staff and make sure all or most new hires have at least some experience with Revit. Most junior staff are well-versed enough in software to pick it up on their own with the help of a more experienced person, just allow for slower turn-around time while they are learning.

Good luck!

Thanks for the good ideas. Are you seeing an increase in productivity from CAD? Can you name one thing you would have done differently?