Yep, I'm sure that definitely has something to do with it. Gronk and Amendola have both returned and continue to get healthy, and Dobson has emerged over the past month or so.
Either way you look at it, Edelman is providing us with a much better WR3 game than last year (Edelman 21 catches, Branch 16 catches) and maybe even the past couple of years since Branch's 51 catch season.
Like many other contract situations, I expect it to come down to whether or not Belichick opens up the checkbook a bit more, and whether or not some other team comes in and throws a better enough deal to lure him away. I think he has a much better chance of returning than last year though, as it would seem that the coaches have to appreciate his progression and continued special teams play.