It depends on the Tie Ratios of the softwares. It is entirely possible if Bloodborne had a 50% tie ratio... but that really not likely. All you have to do is look at the tie ratio for Halo 4 and multiply it by the number of Xbox One consoles. At 25% it is possible for Halo 5 to sell 4 million consoles if the Xbox One can hit 16 million by it release.
If Bloodborne (somehow) got 25% tie ratio, then you are probably right.
The MCC has a tie ratio of about 20%.