I just don't see what re-signing Hejda does. He's slowed down for 2 years in a row, and he's not getting any younger. Move him now for a draft pick or a prospect that may be able to help soon. He's not going to be here when this team wins a Cup. Turn him into a future asset. That's what good teams do.
There's plenty of more options on defense than the ones you listed.
What it does is push Guenin and Holden out of a healthy roster, and give them insurance for not getting worse if they miss out on a top D.
He's slowed down a tad, but we're talking about re-signing him and playing him in a lesser role. As it is now he's better than anyone on the Avs in his top line role. Wouldn't it make sense that he'd be better than anyone below him in their role?
Also, I'm not seeing a lot of great options. Outside Sekera as UFA what is there? There's a soon to be 34 year old Paul Martin, and Ehrhoff who turned the Avs down for a chance at a cup, when they actually looked like a good team. The Pens are probably keeping one of those guys, and the other might not want to leave the east coast. There's Mike Green who I'd pass rather quickly on.
After that, you've got a bunch of guys who if you threw into a top line role on the Avs, I'm not really sure how much, if any better they'd be than Hejda. Guys like Jackman, Beauchemenin, Michalek, Franson, and Regehr. Some of them would likely cost more than Hejda too.
Only guy I see outside of Sekera as a UFA that really makes sense is Boychuk, and he's probably gonna cost more than he's worth, and the Isles probably re-sign him anyway.
As for trade, the only obvious options are Yandle, and maybe Emelin or Buff. Those guys seem D men teams might be willing to move. After that it's a guessing game of who the Avs might be able to pry away from someone. Mabye they find someone good, but when you don't see a lot of hopeful targets, that's why keeping Hejda for cheap as insurance might make sense.