I know that OP specifically said he didn't want to hear about "in PCJS I trust", but... I do.
I'm not thinking that they somehow find a magic solution that keeps this team together in it's current form mind you. I believe that they will be able to field a team that is just as competitive. People will be leaving. I know that and I'm at peace with that. As i see it, the only pieces that are truly vital at this point are Russell Wilson and Earl Thomas. They are the lynchpins that allow us to do what we do on offense and defense respectively. To a much lesser extent I might add Russell Okung, Kam Chancellor and Bobby Wagner to that group of vital pieces (Okung mainly because with there we're drafting, we're not ever going to get another opportunity at a LT of his caliber without paying them a buttload of money anyway). I really want to include Sherman into that vital category, and his play more than warrants it, but I think through scheme we would be able to overcome his departure (we wouldn't be as good, but we wouldn't be as terrible as people think).
For everyone else... I think there's going to be cost effective options available to replace them. Now, that's not to say they're ALL going to go. Our FO guys will make decisions based on a cost benefit analysis of what each player brings to that table and make the decision to retain or part with that player. If people are allowed to leave, it will because they weren't worth the money... and I'm okay with that.
People really seem to be up in arms about the possibility of Michael Bennett leaving. I think he's a phenomenal player and would be happy as anyone to hear we found a way financially to retain him, but we have a potentially great successor for that position waiting in the wings. Greg Scruggs is a very similar player to what Bennett brings. He's also a little bigger and a little stronger, so (in theory) he should be able to fill that 5-tech role on a 3 down basis, allowing us to part with Red as well. Or, depending on how Jesse Williams pans out, they might find their way into a similar rotation as Bennett and Bryant had this year. I can see us sending Clem out to pasture (love that guy too) and rolling with a NASCAR front of Cliff Avril and Bruce Irvin on the outsides with Scruggs and McDonald on the inside. We'll survive. I'm not too worried.
We'll be able to afford another year of Sherman and Lynch with the current structure I'm sure. What that allows though is another red shirt development year for Christine Michael and Tharold Simon, who could very well become successors to those particular household names (for a fraction of the cost).
Next year we'll be absolutely fine and should (will) be challenging for another title. After that, there will more than likely be some substantial change, but I can't see us becoming irrelevant. The stars we have NOW were 5th round and up developmental guys. I totally have faith that JS & co. will be able to bring in more guys to supplement the core.