From my own experience of the steady deterioration of competence, knowledge and ability over the last 20 years in the CAA's Safety Regulation Group, I think the estimate of 5 years for the CAA to regain any resemblance to a leading aviation safety regulator, on a par with EASA and the FAA is wildly optimistic.
Bar a few exceptions, including some, I'm sure, that I don't know about, the last competent person left the building sometime before 2010, leaving behind the incompetent time-servers in their own little fiefdoms and silos, unemployable anywhere else. This is certainly true of Airworthiness and AME Training; I have not heard anything complimentary about a Surveyor in the last 10 years; the most typical comments are disbelief that anyone so poorly suited to the job could be employed to do it, usually with an anecdote about the latest stupid assertion from a Surveyor.
That's not to say that the pre-EASA CAA was good; it wasn't. But from that low point it has gone steadily downhill since the UK joined EASA, and I just don't see how they can recover to become a top rank independent Regulator in less than 10 years, ie the minimum time needed to recruit, train and develop through experience the expert staff it needs.
Mind you, if the UK loses much more of its design and manufacturing capability there won't be much to regulate and approve there; and if UK-registered airlines keep failing the same goes for Flight Ops and Airworthiness as well. There will always be a few airports to watch over, but perhaps not so many as before.
I'm no fan of EASA, but the thought of the present bunch of oxygen thieves in the CAA taking charge instead makes me very glad I'm out of it later this year to spend more time with my boat.