The K2 BT was/is a transition product, something many manufacturers do.
For example AKG created the K702 65th Aniversary model headphones with limited 3000 units, as an improved version of the standard K702 cans. Those 3000 units quickly got sold out and the next year the manufacturer launched K712Pro, which is the same headphone as the limited K702 Aniversary, but this is with unlimited production and with different color scheme, plus higher price tag. And to no surprise, a crowd gathered on the head-fi forums to throw eggs at AKG for doing this.
The only difference with Roksan is the K2BT didn't sell out yet in the stores so it runs along with the K2 and K3 untill it sells out. The K3 got new loks and higher price tag, so it's not competing with the K2BT as the same product. Everyone complained how K2 had a dire design and didn't suite everyone. Well problem solved with the German made K3 plates. It's an improved K2 amplifier + BT connectivity + with better looks. I'm not surprised it costs more.
There is a standalone full 430mm wide K3 DAC, so adding a DAC facility in the K3 integrated wouldn't be the most clever way of doing things.