I still think Ertz has 2-3 years left in him. Despite having a fast TE 40 (4.67) and being a bigger guy (6'5, 250) he really plays a finesse game. He's a great route runner who goes down on first contact.
Last year was similar to DeSean Jackson's 2012 non-holdout, non-caring contract year. He mailed it in trying to avoid an injury before the next contract. Ertz did get banged up, but I think it he used that to avoid further injuries.
Is he worth trading? Not for your team. You'd trade for Ertz knowing he wants an extension. Why not just keep Graham who gives you comparable production for what I'm guessing would be less money.
The rumored landing spot for Ertz has always been Buffalo. They need a TE to work the middle and he'd be perfect. Not sure if it will happen, but it should.