Its not too early to write them off...but at this point they are lotto tickets. As I said, the data on Age 18 and Age 19 Breakout players being real deal collegiate and pro WRs is pretty sound (please look it up, its a good study). Now once you get to Age 20, you're just a lotto ticket. Lots of WRs develop late, but they aren't your R1, R2, or even most R3 type WRs (again, there are exceptions, especially once you get into Day 2, look at Old Man Velus Jones who got drafted last year in R3 at 45 years old).
At this point, Keyshawn is a lotto ticket. All of our WRs, IMO, that are going into 3rd year and up are lotto tickets...X included. If you go into the year with nothing but lotto tickets...that can be a tough year.