Actually that's not true at all. The biggest knock on our WR core for years has been that we have depth... we just don't have anybody who separates themselves from the pack in terms of quality talent. If all of your receivers on your roster are near the same caliber of talent, then by definition, you have depth, because it means that if one of your "starters" goes down, the replacement level player is nearly as productive.
The REAL issue with our WR core is exactly what the FO has told us it is... we have no possession receiver who can work the middle of the field and be effective on third downs or in the red zone. That's the type of receiver we need. The reason why a Wallace/Perriman combo isn't exactly thrilling is because they both run similar route trees and have similar skill sets, and neither is a guy you trust to go over the middle and make a tough, contested catch in a critical spot in the game.
That's the type of guy we're going to look to add. If its a first rounder, great. If its a veteran, cool (I wouldn't prefer this). If its a mid-rounder, good.
Your third WR is typically going to play somewhere around 50-60% of the snaps. Aiken played 52% last year, Perriman 43%. Even Steve Smith only played around 64%, so the drop from him to Aiken wasn't nearly as big as people think.
If we're in that position, that's what I'd expect to happen. Wallace will lead the receivers in targets and playing time, and Perriman and a third receiver (not yet on the roster most likely) will be playing about 2/3 or so, split among them. I don't see anything we do, including a first round WR, changing that. I don't think you're going to see Wallace and another player both playing like 90% of snaps. Think you'll see a steady rotation of guys.