The 24-year-old has spent seven seasons with the Force after making his debut in 2006, the same year the franchise became Australia's fourth team in an expanded Super competition.
The club has never reached the playoffs and the 2012 campaign was one of their worst, finishing second-last on the overall table with just three wins from 16 games.
The lack of finals action has reportedly prompted Pocock, who skippered the Wallabies in Tests against Scotland and Wales this year, to find a more competitive team.
Speculation has been rife that Pocock will on Monday commit to the Brumbies, especially since their outstanding young flanker Michael Hooper is switching to the Waratahs.
The Force gave credence to the rumour when they released a statement saying they'd failed to convince Pocock to remain in Perth.
"It is with considerable regret that RugbyWA has learnt of David Pocock's decision to leave the Western Force at the conclusion of the 2012 Super Rugby season," the statement said.
"For the past six months, RugbyWA has done everything within its power to retain his services as a leading player within the Western Force.
"David's concerns were principally around the club's inability to recruit high-profile players with this challenge highlighted by the recent opportunity presented to (Wallabies and Reds halfback) Will Genia which ultimately was unsuccessful in bringing him to WA."
"While we are disappointed with his decision, we wish David well.
"David will always have a special place at the Emirates Western Force and should the opportunity arise down the track for him to return, we would welcome him back with open arms."
Pocock's departure is a massive blow to Force fans, who have had to deal with the retirement of veteran second-rower Nathan Sharpe this season, the loss of star Wallabies utility James O'Connor to the Rebels last season, and coach Richard Graham signing with the Reds mid-2012.
Pocock played 69 Super Rugby matches with the Force and replaced Sharpe as captain this season.