A trade up in the 1st round to select a WR has to be coming.
It could be, but it's not a requirement. And the Bills have other needs which would line up as BPA at pick 28 or even a trade up.
If you look at elite QBs as the progress, the better they get and older they get, the less they need the "elite #1 receiver." Early on, you want to surround a young QB with targets. Later, as the QB learns to read defenses and can get what he wants without an elite receiver, the less they need the elite WR. That was the case for Brady for sure, and it's becoming the case for Mahomes.
Brady was statistically best when he had Welker and Moss, but once the Pats went to Gronkowski and then eventually Edelman. Mahomes probably needed Hill early on, but eventually grew to not need a true #1 receiver, and just throw to the open player.
Offenses are actually at their best when there isn't a true #1 wide receiver demanding the ball. OCs with a bunch of #2 type receivers don't have egos to feed, and can just let the elite QB throw to the open man. Allen forced a lot of footballs that should've went elsewhere.
The other trend I see with elite QBs is having the top receiver as the tight end. Brady had Gronkowski, Mahomes has Kelce. I've been writing this for months, but Kincaid is going to be the top receiver by November, with or without Diggs.
So Beane may trade up and take a WR. But I don't think he has to. Adding receivers with an elite traits or two (Troy Franklin, McConkey, Walker, Rice, etc) who also doesn't need to be fed the ball, will get the job done.