So that would be only 2M coins.
If every DRK in existence right now was tied up in a masternode, there would be 4399 masternodes.
At lowest reward (safe to assume) currently that would be ~0.131 DRK/MN/day ~ 48 DRK/year
At 2000 MNs (a bit more realistic) it's 0.288 DRK/MN/day ~ 105 DRK/year
At 1000 MNs it's 0.576 DRK/MN/day ~ 210 DRK/year
At 500 MNs its 1.152 DRK/MN/day ~ 420 DRK/year
Going with 1000 MNs as what IMO will be a good rough guess, each of my MNs will bring me in about £1500/year at current prices of 0.02DRK/BTC(@£350)
1000DRK currently costs ~£7000 so that's a 21% return per year. *At current prices, which are unlikely to remain this low if all goes well!*
Plus with so many DRK/fiat exchanges popping up, the price of BTC will become increasingly less relevant to DRK holders.
DRK is not an alt, it's a financial apex predator...