It isn't very easy I'm told- The modules like their space. Also an FM module works happily across the globe, any DAB equipped AVR would need to carry Band III and L Band and still have FM if you hoped to sell it in the US.
The tuner functionality on an AV receiver tends to take the back seat in the majority of AV user needs imho. One less box is always welcome for those who lack space on their racks, but for the most part, a lot of people tend to go for a dedicated tuner.
I myself will probably go for the Pure 701ES, I think this model does both FM and digital radio, and I trust the brand too (used to have a videologic digitheatre DTS as my first surround sound setup ). I still think an all bangs and whistles receiver will show up once the fever over DPL IIx wears out Or maybe I'm just being cynical
when i asked the rep about this 1 month ago he couldnt guarantee that harmon would be bringing out the upgrade module in the uk. i have since read reviews about dab that suggest the audio from sky plus is better so have put that idea on hold for now.
You could be waiting a long time as I wouldn't expect any of the main manufacturers like Denon or Yamaha to be interested in producing a DAB tuner integrated.
Why go to the expense of developing something just for the UK market which is relatively tiny compared to the rest of the world.
Remember alot of the products we see here are the same as or derived from products developed for the States and the rest of the world.
The only companies that may go down this route might be Arcam, HK (European division) and possibly Onkyo.
Of course more highend UK manufacturers like Tag (Which I believe has just been bought out by Quad / Wharfedale - not really UK owned) do see some sort of market here and have developed accordingly although you do pay for their research.
All in I would be surprised to see that many far eastern receivers with built in DAB.