I fully expect that to be coming. On the current model, packaging DCT into the existing gearcase is probably impossible, but someday when the (now 16 year old) GL1800 gets replaced, I expect to see it have DCT. I would also not be surprised if it was offered standard with DCT, with a manual transmission not even being an option.
The only real challenge is where to add yet more buttons on the handlebars.
I might have to add another pony to the stable if/when they do that !