Seahawks true available cap space accounting for all players on the roster sits at $9,214,517.
They have exactly 61 players on the roster at present, so 29 more to add to get up to 90.
Assuming Byron Maxwell will still be resigned
Adding on the bottom two players when the cap goes from 51 players to 53
Paying for the draft picks (assuming about 6 of them make the roster)
That leaves them with around $1,000,000 going into the season to sign players to replace guys going on IR.
I can say with 100% certainty based on this that more roster moves will be made.
Avril could still come off the books and Earl could be moved.
If Avril is cut/retired but Earl stays, they'd have roughly $8,125,000 in available room.
If Avril stays but Earl is moved, they'd have roughly $9,500,000 in available room.
If Avril and Earl are both not on the roster they'd have roughly $16,625,000 in available room.
Another possibility if Avril and Earl do return is a Duane Brown extension. Although if that was their way of getting enough money to cover themselves during the season, it isn't ideal. They'd have to steal from Paul to pay James on the 2018 cap figure for Brown which isn't ideal.
Unless changes to Avril and/or Earl happen don't expect a Frank Clark or Tyler Lockett extension this summer.