The "gains" are the fact that .uk is going to happen anyway. Everything I've read so far on the subject suggests that Nominet is too far along and too invested in the idea to scrap it completely.
So the "win" in this situation is to get the best possible outcome for businesses (they are the ones that .uk is designed for) from the range of scenarios that are in fact plausible.
As I've posted before, the logic is water-tight: Nominet has promoted .co.uk as the trusted extension for businesses since year zero, and continues to do so right now over on
http://www.agreatplacetobe.co.uk/ Since they want to introduce .uk with broadly all the same "attributes" as .co.uk (plus some extra security features) and using the same sort of pitch (the extension for business, trustworthy etc.) they're using for .co.uk then logic MUST dictate that .co.uk owners deserve first crack at it.
Think of .co.uk as a car, .org.uk as a bicycle and .me.uk as a skateboard. They're all modes of transport, they'll all get you from A-B. Now .uk comes in, and it's a different kind of car. Which of the 3 groups should get to benefit from it?
I also firmly and sincerely believe that Nominet can't "erase" the value in .co.uk just by launching .uk. There will be 2 "desirable extensions" for business, not 1, if .uk goes ahead - you can't undo 15 years of branding by millions of businesses just by wishing it. So why should a business that has already secured a great .co.uk domain throw that away for a lesser .uk one? (this assumes Nominet doesn't grandfather them in automatically).
Sure, IF a business gets both it's decision time - and I believe the fairest is that they should have that choice - but it's the work of seconds (and free) to point 2 domains to 1 website and be done with it. There's no need for a "rebrand" beyond that - people will be able to find the company no matter which "variant" they try!