In November of 2010 I wrote about Digital Mars wanting to integrate D language support into GCC and in October of last year it was brought up again. Neither time was the D language support merged for one reason or another -- like whether there would be an active maintainer, some technical issues, etc.
As seen from the gcc-patches mailing list, merging GDC is being tried again for GCC 4.8. Will it get pulled this time? We'll have to wait and see -- so far the responses have been minimal.