I would actually prefer DK Metcalf over Brown and Foster if his play were to match his physical stature; Bills don't just need speed: they need speed, size, and strength on the outside, Metcalf is just that.
It's the drops, lack of fluidity that his 3-Cone Drill suggests he has, and the fact that he doesn't strike me as the naturally, dominant type, that has me really skeptical at the moment.