Unless Daniel Jackson or one of the newcomers turns out to be the next Bateman, I'd be very surprised if Douglas wasn't the #3 WR and a starter next year. He was clearly one of only 4 WR's we had that the staff felt comfortable actually throwing their way and one of them is graduating.
Personally I think there is a good chance he has a 600 or so receiving yards next year, similar to what Carrington Thompson did in 2016 at WMU. In Fleck's third year at WMU, they had two 1,000 yard NFL receivers in Davis and Bravemen. Then Bravermen graduated and Davis ended up having a 1,300 yard season, Michael Henry had a 700 or so yard season, similar to what i'd expect out of CAB and Thompson had a 600+ yard season. I think next year Bateman is our Corey Davis, CAB is our Michael Henry and Douglas is our Carrington Thompson.