I think 6 WR's will be kept on the team.
John Brown
Cole Beasley
Zay Jones
Robert Foster
Andre Roberts
Isaiah McKenzie or Duke Williams.
Brown & Beasley are locks, not to mention veterans. They will be valuable to the Bills.
I do not see the Bills giving up on Jones & Foster. Jones is frustrating with the drops, but I think McDermott has confidence in him. Foster is only in his second year, and he still has potential to grow.
Roberts is a returner, but the Bills have been using him as a receiver too. Unlike Brandon Tate, it looks as if he will be used more than just as an emergency receiver.
That leaves McKenzie & Williams. McKenzie has shown that he can be reliable. Williams is a big target, and that touchdown grab against the Panthers was a beauty.