Hi, 237SJ
I suspect that the switchover to totally-digital radio is a long way off yet. Although a theoretical date of 2015 has been set, it will almost certainly get put back. (The UK Government signed an international broadcasting agreement, committing us to completing the digital TV switchover by 2001. So long delays aren't exactly unknown!).
There are still a great many 'unknowns in the equation'. It would make sense, in many ways,if the UK joined the rest of Europe and adopted DAB+, but that would make all existing DAB radios redundant. Further, a new system (called DRM = Digital Radio Mondial) is currently being trialled, which permits digital radio to be broadcast over long distances on Medium Wave). So it's hard to predict the future of radio in the UK. However my guess is that the situation is fairly stable at the moment. (i.e. we'll keep the existing digital stations, plus those which switch from FM to digital but we won't see many new stations).
Chris