If Pickens' next season looks like his last three - 60'ish catches, 1000 yards, lots of big downfield plays, and fights with the other team - I figure he'll get a contract paying about $25M/yr.
To throw out some comparisons, Tee Higgins is getting $29M/yr, Jaylen Waddle is getting $28M/yr Devonta Smith is getting $25M/yr, and Chris Godwin is getting $22M/yr. They're all high-end WR2s consistently putting up around 1,000 yards per year, and they probably have the talent to do more in a feature role.
Pickens isn't as complete of a receiver as Higgins, Waddle, or Smith - he's solely a deep guy, while they're all 3 level beasts - but he's also younger and healthier than Godwin. I think $25M sounds about right.