While the Seattle Sounders can add a Designated Player in the upcoming transfer window, they are also looking towards next winter. After the 2017 season the team holds an option on Clint Dempsey’s contract according to Sam Stejskal at MLSSoccer.com’s conversation with President of Soccer Garth Lagerwey.
Stejskal also relays that Dempsey will either be a Seattle Sounders DP in 2018, or a Free Agent. If the Sounders were to decline Dempsey’s option, he’d immediately become the highest-profile free agent in MLS history.
Assuming he's fit and playing anything like he has been, though, it seems a reasonably safe bet that the Sounders will want to bring Dempsey back.
Dempsey is still a key part of the United States National Team and could make his fourth World Cup if he continues his form in Red, White and Blue.
The forward/midfielder leads the Sounders with four goals and also has an assist. He is the 31st scorer in league history and
4 5th among active players (Chris Wondolowski, Kei Kamara, Bradley Wright-Phillips and Chris Rolfe are ahead of him).
Clint has a bit of unfinished business. He has yet to play in an MLS Cup he’s won. He was sidelined with heart issues when the Seattle Sounders won in 2016. His two appearances with the New England Revolution ended in losses.
Between the goal of playing in and winning an MLS Cup, his pursuit of Landon Donovan’s American goal-scoring record and going to the 2018 World Cup there is no indication that Dempsey would retire at the end of 2017. He will either be a DP in Seattle, or the most sought after free agent in league history.