There's no fixed date to switch off the analogue (FM and AM) signals yet.
However, a car hi-fi with DAB (Digital Audio Broadcasting) is still worth considering. You get a great choice of stations, and some that were previously available only on AM can be heard in much better quality.
DAB is now available at least as an option on many new cars. Alternatively, you could invest in a DAB adaptor, which works in much the same way as radio-based iPod adaptors: it tunes into an available FM station on your car's standard-fit hi-fi.