Similar to the twins, because he's still a good player it would leave a hole on the roster, though of course he would also free up some cap space. Unless he has a fantastic year, I expect re-signing him would be pretty cheap though.
The Sedins were about 37.5 when they played their last game and if Edler retired at the end of this year, he'd be about 35, so he'd definitely be leaving years on the table. I'd say he'll look for a 1- or 2-year deal. If it's 2 years, I suspect that'll be the last one of his career. As much as I'd love Edler to continue to push Canuck records, I don't see him playing late into his 30s or til 40, though I do believe he'd be capable of it.