The striker informed manager Phil Parkinson of his decision having handed in his 14-day notice to terminate the end of his contract, which has been appealed by the club.
The Northern Ireland international wants to see out the two weeks before making a decision on his future with several clubs having been linked with a move for the 28-year-old.
Magennis’ move comes despite wages being paid to contracted Wanderers players on Friday as the final details of the Football Ventures consortium’s takeover are ironed out.
His refusal to make the trip to Adams Park could in theory lead to some form of punishment being laid down with a fine of two weeks’ wages one option available.
That decision will likely lie with the new owners once the takeover is completed.
Magennis may not be at Wycombe but Parkinson will be able to use a smattering of senior players – Remi Matthews, Jason Lowe, Luke Murphy, Dennis Politic and Erhun Oztumer among them – supplemented by youth team players in the League One opener.
Once the change of ownership is finalised the club will be looking to sign around 15 players before the end of the transfer window, several of those already lined up.