In comparison to other skill positions, the top end of the tight end market isn't nearly as inflated. While the likes of Calvin Johnson, Larry Fitzgerald, and Adrian Peterson signed contracts that average annually well over 10 million a season, the tight end market is capped by the standard of the deals Vernon Davis and Rob Gronkowski recently signed - roughly 7 million a season. While Dustin Keller is a very good receiving tight end and would make almost any offense better, he certainly isn't on the level of those players. Despite that, if he were the only tight end of note on the market, he would probably sign an inflated contract paying him more than his worth and closer to that upper tier of contracts, pricing the Jets out of a potential re-signing. What could work in the Jets favor is that Dustin Keller is one of several tight ends of similar value on the free agent market. Keller, Tennessee's Jared Cook, Fred Davis of the Redskins, the Giants' Martellus Bennett and perhaps Baltimore's Ed Dickson are all receiving tight ends ranging from ages 25 to 28 that will draw interest from teams as a starter. For a team in the market for a tight end, there are several options of a similar quality and thus much less incentive to overpay for one particular tight end over another.
Granted, Dustin Keller is still the best tight end available and thus still could sign the best deal - likely to be similar to the deal signed by John Carlson last year(5 years, 25 million). The Jets may be able to sign Keller to such a deal, though it'll come down to he versus Landry as they will not be able to retain both. But should the Jets lose Keller, they could still be in the market for a decent replacement. Bennett and Dickson for example would be considered a little risky but should be available at a decent price - Bennett only has last year with the Giants to show for his receiving ability and Dickson is a naturally gifted young player but one that has yet to put it together. Alternatively, if the Jets don't prioritize signing a natural receiving tight end a decent stopgap like Anthony Fasano could be in the cards with Cumberland seeing an expanded role(it sounds like he'll be returning).
With some luck, the Jets should be able to find somebody in the free agent market to come in as a starter, whether it's the incumbent Dustin Keller or someone else. Maybe Idzik will push heavily for Landry and look to sign a stopgap like the aforementioned Fasano. If nothing else, the Jets will have some options.