Watkins will be good for 60+ receptions and over 800 yards. He should end up with about 8 TDs. Other receivers in the group will soak up 20 to 30 receptions and 300 yards, along with 4 TDs. The loss of Adams to the overall passing game will be minimal. In a way, beneficial, because there will be more than one receiver that has to be covered. The Packers, and Rodgers, had started to rely way too much on the Rodgers to Adams connection. It was comfortable, and an easy choice. Now the ball will be spread around a lot more.
Sometimes a major subtraction can be a major addition, because it gives the Packers two picks early in the draft to help retool the WR corps, and improve the team in another position. Having two firsts and two seconds is pretty darned nice.
As far as Watkins and injuries, the entire team he played on was an injury waiting to happen. I think they were either the worst in the league, or close to it this past year. Sometimes it's not the player, it's the system they play in, that exposes them to more potential injuries. Not saying that was definitely the case, but it could be a factor.