I am somewhat reminded in this thread of Sean Connery saying he would never do Bond again! I think that the chances of GR.9 dropping weapons in anger are still very good for the old workhorse. Politically any government is going to find it very hard to scrap carriers that have already been started - I would anticipate that the potential Trident replacement stands a far greater chance of being abandoned.
As an insurance policy for the future the Harrier stands a good chance of surviving -in terms of technology, advancement of it's capabilities hasn't been abandoned and the airframes are capable of easily being advanced beyond 2018 -it's been looked at already.
So in essence I would say that F-35 has little or no future and the likely hood of the new carriers having a compliment of Harriers is very high.