The former Arsenal star is one of those to have expressed concern at the current state of the club, as the Gunners slipped out of the elite.
Merson knows it will be a long road for the club back to the top, if a change in the dugout is made.
“Arsenal are a million miles away,” the ex-England international told Sky Sports.
“This is a four-year project now, a four-year project and about £500m to get anywhere near back to where they were.”
Merson added: “You’re going to get a Man United situation when Sir Alex Ferguson left.
“The next manager will come in, it won’t work out, they’ll get rid of him within a year. Then another manager will come in.
“Things can’t get any worse to be honest. They’re sixth and that’s where they’re going to be.
“Surely it couldn’t get worse than that. I look at the other teams and no one is going to catch them, I don’t see anybody else coming above Arsenal in sixth.
“But this is Arsenal Football Club and they’re becoming an also-run, an also-run.
“They’re Everton, they’re Everton. We’ve had this with Everton for the last 15 years.
“They’re the next best team out of the top six, they’re not going to get any better, and this is what’s happening with Arsenal.”