Probably realised that the paint has just dried in the newest buildings at Blandford and thought it was time to move on again. Mind you, a sensible location in the middle of the country... it'll never happen That or the Infantry are after another posh armoury
I heard about this a couple of days ago. Cosford's big problem (apart from the obvious- being near Wolverhampton) is that to expand, they'd have to get permission to use green belt land. St Athan on the other hand will have tons of spare room due to collapse of DARA and the entire Picketston site to the North.
On the other hand, 1 PARA are due to move there next year- but then again, that'll mean that property values will come down a bit.