I don't think that's true at all, at least with a new coach it`ll be a fresh start and that person might have some concept of how to run an offense.
The defense is already there, if you can get a guy in there who knows offense, make a few acquisitions and get a QB in there (rookie or FA vet) at least it`ll be one year of building as opposed to one year of destroying.
Think about it, new coach comes in goes 8-8, that's a positive. Rex stays goes 8-8, that's a negative.
They also need talent. Unless the GM hits a home run on every draft pick, they're not gonna get a major infusion of talent that will make up the difference. They kinda have to take the hit next year and then open the floodgates in 2014 when they'll have a shytload of money and (hopefully) a new QB.
I don't expect anyone to come in, take what we have, especially on offense, and somehow make massive improvements with a tougher schedule. They need a new QB, RB, and TE. The Colts got a new QB, TE, WR, and RB and it worked, but they hit on every pick, especially Luck. Right now the Jets just need to fill as many holes as possible, deal with one year of God knows who at QB (probably Fez) and then have the new QB walk into a developing yet promising situation with a new coach + staff. Next year though, NFC South + AFC North + AFC East = waste.