I would suggest it is another example of senior BBC management meddling in the broadcast operation which is making a lot of people unsettled and unhappy. You see it with Morning Live which is working perfectly well but is moved, not for creative purposes but for political ones. Its very unhealthy. I don't know if UK news will work financially and be welcomed or understood by the UK public. Maybe he will join his old friend Ms Burley there. It will be interesting to watch.
Whilst he is a great loss to the BBC no one is bigger that the corporation and no one is indispensable. The BBC can make a star but it doesn't last forever. Good luck to Simon he will be missed at the BBC.