Whoever takes over at Old Trafford has a hard act to follow, Hamilton said -- but Manchester United will have been planning carefully for this moment.
"There will definitely be someone in place, I think -- the big question now is who that person will be because it's been kept a secret from everyone until now," Hamilton said.
Whoever it will be has a daunting, if exciting, prospect ahead.
"It's the largest football club in the world, it's the biggest management job in the world, and on top of that is the task of following the most successful manager in the club's history," Hamilton said.
While Moyes is favored for the job after more than a decade with EPL club Everton, other names on the bookmakers' list include: Portuguese coach Jose Mourinho, formerly of Chelsea and currently at Real Madrid; Borussia Dortmund's Jurgen Klopp; Michael Laudrup of Swansea City; and former Manchester United striker Ole Gunnar Solskjaer, currently managing Norwegian team Molde.
Fans' thoughts are bound to turn quickly to the 2013-2014 season, starting in September, as Manchester United prepares to defend its domestic title and attempts another win in Europe.
As recently as last week, Ferguson suggested that he was fully involved in those future plans, promising the club would be "competitive" in the summer transfer market.
Speaking to Inside United, the club's official magazine, Ferguson said: "Hopefully the players we bring into the club in the next year or so will be of the quality we need."
Manchester United coasted to this year's English Premier League title with a 3-0 victory over Aston Villa in April, with four games in hand.
Ferguson is due to undergo hip surgery this summer, according to UK media reports, but it's not clear how much of a role health concerns have played in his decision to stand down.
"I think retirement's for young people because you can do something else. When you get to my age, if your health is good, you like to work," he told CNN in a 2010 interview.
Sports writer Mihir Bose said he was surprised by the timing of Ferguson's decision, despite his upcoming surgery, saying he had expected him to carry on as manager for another couple of years.
Ferguson -- who is seen as a kind of father figure by some of the young players he developed -- has "that ability to reach out to people," said Bose, but he is also a skilled political operator.
"He could be delightful but he was a man who made sure that he controlled the agenda," he told CNN. "If you crossed his path he made it very clear that he controlled everything at Manchester United."
Those who got the famous "hairdryer treatment" -- loud shouting directly in someone's face -- included many sports journalists over the years. Ferguson would also refuse to speak to reporters if he didn't like what they said.
Despite that thorny relationship, Ferguson will be remembered as an iconic figure in English football history, said Bose. The big challenge now is how Manchester United will manage the transition to ensure continued success, he added.
'A sad day'
Former Manchester United and Denmark goalkeeper Peter Schmeichel told CNN he was still trying to make sense of the news.
"It is a sad day. I'm shocked, I'm sad, I'm disappointed. It's a day I think everyone who loves Manchester United, everyone who's worked with Sir Alex -- it's a day that we've been expecting, but I have to be honest I didn't think it would be now -- I thought it would be a couple of years down the line."
Schmeichel said he was certain that Ferguson had not been forced out but had made the decision himself, given his record of success and changes already happening on the club's board this summer.
He paid tribute to Ferguson's knowledge, skills and philosophy as a manager, particularly his ability to bring on young players.
Internationally known footballers like David Beckham, Ryan Giggs, Paul Scholes, Gary Neville and Nicky Butt were all created by Ferguson, Schmeichel said.
"He is the best manager in the world and he's the best guy as well. He's a really good friend as well."
Ferguson's talent has been in managing players individually rather than as a group, Schmeichel said.