Parker, Agholor, Bourne, Meyers, Thornton, Nixon, Wilkerson...
Now cut two, they won't roster 7 WR's. And before you begin this exercise remember this:
Agholor is making 10 million dollars and has no contract next year. They can open a lot of cap space by trading him. He also has a solid reputation (except here) and despite his contract he is a reasonable one year rental for a contender who injures a WR in preseason.
Meyer's wants a contract for next year and probably thinks he deserves close to the four years 72 million that other slot WR Christian Kirk got... and good god that's a massive overpay. Even if he thinks he doesn't deserve that much, it has to be close, the market has been set.
Also consider this... Thornton, Nixon and Wilkerson are on rookie deals... they cost next to nothing and are locked up for years. Even if they become All Pros, they still will be cheap until their rookie deals run out.
They could carry 6 WR's but probably won't, not unless at least two of them become serious contributors on special teams. A team that can only roster 53 players and only activate 48 players on game day can't have seven guys standing around doing nothing but offense, somebody has to play special teams.
Even if they have more, the most WR's they'll have on the field at a given time is 4 or 5 max... more isn't better.