I have a strong suspicion this will go the same way as the DAB switchover
And I know I'm late to this, but the same argument applies, to an extent. It's a solution in search of a problem. DAB is great an' all, but the 20MHz (88 - 108) of VHF that would be freed up by switching off all FM transmissions is not a fat lot of good for anything except broadcast radio. I suppose you could convert it to DAB :-)
This may be one of the reasons LW persists. The 140kHz or so of spectrum (150 - 290?) used for broadcast ain't much good for anything else, and in fact excels at national-scale broadcasting.
And as for that aerial alongside the M5 at Droitwich. Wow. If LW ever is switched off, I hope they list that structure so that it's saved for the sheer history. Just out of interest - I was looking for the thing just now on Google Streetview, and it almost seems as if they've tried to blank it out. It's visible in the distance in some views, but as you get closer it's more and more difficult to see. Maybe it was misty that day; it's visible from different angles.