Skipper Van Persie revealed on his official website he would not extend his contract, which runs out at the end of the 2012-13 season.
The 28-year-old cited his desire to win trophies as a key reason for his decision, with Arsenal yet to win any silverware since 2005.
Despite that Merson believes Van Persie, who scored 37 goals in all competitions for the Gunners last term, will live to regret leaving Emirates Stadium and warned that he would be "slaughtered" by Gunners fans if he is unable to secure a move before the new campaign.
"Not many players leave Arsenal, very rarely, and don't regret it. It's an unbelievable club," Merson told Sky Sports News.
"It's perfect. I'd have liked him to stick it out.
"I'm a bit gutted really. He's burnt his bridges. If he comes back and they don't sell him the fans are going to slaughter him.
"They'll be devastated. He's a top-drawer player. World class."
Big-spending Manchester City loom as the most likely suitor for Van Persie as they look to further strengthen after their breakthrough Barclays Premier League success last term.
Former Gunners striker Alan Smith does not believe, however, that the Dutchman was swayed to turn his back on the club by the riches the likes of City can offer.
"From what I have heard from people close to Robin he's not motivated by money," he said.
"I think at his age, he's 28, it's about winning medals. He's in his peak years now. I truly believe in this case he wants to win things in the next few years when he can.
"That doesn't reflect well, of course, on Arsenal. It's really disappointing from Arsenal's point of view.
"But Robin van Persie is looking at the next few years when he's 28, 29, 30; he thinks they can't win trophies. You don't want to say it but you probably have to agree with him."
Smith fears Van Persie's departure is set to widen the gap between the Gunners and those clubs at the top of the Premier League.
While Wenger has already brought in Lukas Podolski and Oliver Giroud to boost his forward options, Smith is unconvinced they can match Van Persie's influence.
"He's got a lot of hard thinking to do now, Arsene Wenger," he said.
"He's brought in Giroud and Podolski but can they replace the 37 goals he got last season? They are going to have to for Arsenal just to stand still let alone move forward.
"It's a double blow for Arsenal because they've also lost a captain, and a good captain too.
"It's going to be very difficult to make up the points they trailed Manchester City last season.
"I'm not saying, though, that they've got no chance at all."
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Former midfielder Ray Parlour believes Van Persie had made up his mind to leave the club before the end of last season.
"I think he knew three or four months ago that he wasn't going to stay," he said.
"That's football these days. People move on quickly. Arsenal have to accept it and move on."
With Van Persie set to fetch top dollar Parlour has urged Arsenal to immediately reinvest the money in the squad.
The Gunners hierarchy were criticised for failing to spend following the departures of Cesc Fabregas - also skipper when he left for Barcelona - and fellow midfielder Samir Nasri.
Parlour is hopeful that situation will not occur again, adding: "There is talk he could get £25million to £30million. If that is the case it has to be invested straight back into the club.
"When Fabregas and Nasri left the money wasn't invested back in. They need to spend the amount they get and maybe more as well.
"Maybe they can get two or more players with this money."