There's absolutely no chance that Rex could get a head coaching gig anywhere next year, so why wouldn't he take a 1-year deal? It's either that or hope he can get a defensive coordinator job somewhere. I think the perception of him today is that he's a good coordinator, but comes with enough baggage that most teams would think twice about hiring him.
Rex will probably get offered a head coaching job elsewhere next year. Not for sure but probably.
Idzik isn't going to offer him any deal, so its not like it will be too much of an option for Rex to stay in NY on a 1 year deal. Idzik will bring in his own guy. Rex's decision to play Sanchez in the 4th quarter of a preseason game where Sanchez ended up getting hurt killed their season (cause Geno Smith sucks more than Sanchez sucks) before it started....he wrote his own ticket out of NY right there back in August.