The Seahawks announced two more cuts this morning, releasing rookie WR Donavon Kemp and terminating the veteran contract of Will Blackmon. Kemp hits waivers, and I believe that Blackmon simply becomes a free agent, free to negotiate with any team. He'll likely find a new job somewhere after putting some good 'tape' out there this preseason, including a nice pick (which was called back due to a pass interference penalty, but was nice nonetheless) in last week's game.
Kemp will likely revert to the ghost roster and could have a shot at the practice squad (though I think the Hawks might be higher on guys like Arceto Clark and Perez Ashford, but we'll see).
These two moves bring Seattle's active roster number to 79. To get to 75, my guess is that they'll place Greg Scruggs, Percy Harvin, Tharold Simon, and Korey Toomer on the reserve/PUP list, which means each of those guys will have to sit out at least the first six games.
UPDATE: Seattle has done this - Harvin, Scruggs, and Simon head to the reserve/PUP list and Toomer is assigned to the reserve/NFI list. (Note: Seattle's roster now sits at 75).
Scruggs, who tore his ACL over the summer, is notable in that the Seahawks apparently believe he has a shot at returning at some point this year. If he cannot, he can still be placed on the IR down the road.