The 22-year-old striker is in talks over a £9 million transfer to Selhurst Park, but will the Black Cats come to regret selling?
As the youngest forward in what is an ageing strike force of Steven Fletcher, Jermain Defoe and Danny Graham, few of which convinced much last season, Dick Advocaat is letting go of the one player that would likely get better over the next couple of years rather than worse.
The £9 million fee reported by Sky Sports is a large amount, and allows Sunderland to reclaim much of the fee they paid Ipswich for the player in 2011, which BBC Sport said was up to £12 million depending on clauses met.
The 22-year-old is now undergoing talks at Selhurst Park to decide if he wants to make the move, but it is clear that he is not a player Advocaat is planning to utilise next season.
Wickham has long been expected to fulfil his potential to become one of England's best forwards, and though he has certainly not done that in his time at the Stadium of Light, he has provided flashes of sustained quality during his stay at the club.
Most notably during the 2013-14 season, after a couple of loan spells of which one was particularly rewarding, Wickham returned to the Black Cats with the club in dire straits down at the foot of the table.
Their turnaround under Gus Poyet is one of the great Premier League escapes, and few players contributed more than the youngster, scoring braces against Manchester City and Cardiff, and a goal in the famous win at Chelsea, on the way to being named player of the month.
Another difficult season was in store for Sunderland and Wickham last year, and the former England Under-21 star was unable to reproduce the form he managed just months before. And that is enough to apparently convince Advocaat that he is worth cashing in on.
But Wickham is only a few months younger than Harry Kane, who few were paying much attention to this time last year.
He still has all the potential to become a quality Premier League player, though it looks like that won't be at Sunderland.
Palace may now be the ones to benefit, if they can bring that ability to the fore. And with a playmaker as impressive as Yohan Cabaye in the middle of the park, and with equal creativity on the wings, it wouldn't be a surprise if Alan Pardew suddenly finds he has an England international on his hands.