If it goes ahead..
I do believe most companies will try and register their .uk
I do not believe most businesses will use it though, they will just redirect the .uk to the .co.uk, especially in your scenario if they have to change advertising.. what would be the point in swapping to .uk just to cut out the co, certainly wouldn't be worth the money to change.
Shows how pointless the .uk will be as the security that's been promoted won't do much if you then immediately redirect to an "insecure" .co.uk!