This is what I'm worried about. I am sure they will have some working ahead a version and then have clean up, but there will be a lot of things that will be 3-5 months of work then a feature freeze. That's not really a lot of time to get some major work done. Maybe some of the major features (new file system) would be a multiple year effort, but a lot of things will be sacrificed for time constraints.
With good planning and moving to a more agile development process they may be able to pull this out. Also, being a huge company they can allocate many teams to work on different features.