Well, to start with Audi have indicated that DAB will be available for retrofit when they've sorted themselves out, so worry not.
Next, as mentioned in other threads, the govmint is NOT turning off analogue radio in 2015 - the idea has been shelved indefinitely as it had been met with a tumultuous burst of total apathy and takeup of DAB is way lower than expected.
Er... why would the SAT/NAV fail to work during 2015? As far as I know there isn't any apocalyptic event scheduled for that year (apart from my 64th birthday, that is) so I'm at a loss to understand why you're worried about it.
Edited by: Gromit