The 40-year-old Dutch keeper's retirement has been on the cards for some time and United have been preparing to have to fill some big boots by bringing in Dane Anders Lindegaard who will be registered with the club in early January.
"We're planning for it to be possibly Edwin's last season," Ferguson told a news conference.
Asked if there might be a coaching role for Van der Sar, the manager replied: "He'll be someone of interest in terms of his knowledge and standing in the game, but we haven't discussed that yet."
Van der Sar, who in 2009 set an English league record of minutes without conceding a goal when he went more than 21 hours unbeaten, has been key for United since his arrival in 2005 from Fulham.
Moments of brilliance have been peppered with the odd blunder like the one in October's 2-2 draw with West Bromwich Albion where he dropped a simple catch in a mistake Ferguson said was "inexplicable" but one he would make "the only time in his life".
His cool head at the times when it really counts, such as when he saved Nicolas Anelka's final penalty in the shootout against Chelsea in the 2007/08 Champions League final, are what United will miss.
A modest man, who even when he was setting his clean sheet record was quick to say the secret to his success was hard work from everyone, Van der Sar has helped United to three Premier League titles.
His team mates have often said he has been getting better with age but even if that is the case, Van der Sar knows everyone has an expiry date in the game although he has yet to comment on the issue.
Having been caught out a decade ago when Peter Schmeichel left, Ferguson has been determined to avoid facing a big goalkeeping hole when his current number one retires.
With that in mind, 26-year-old Lindegaard has been training with United in recent weeks and will be registered after the holiday season.
"He is training with us now and that is important," Ferguson said of Lindegaard, who has joined from Denmark's Aalesund for 3.5 million pounds according to British media.
Van der Sar is likely to be between the posts when the Premier League leaders host Sunderland on Sunday.
