I doubt he leaves, it’s a great situation for him here
I think knowing he's Jimmy's #1 WR target has the potential to prolong his career - Kittle is the #1 always, and it's a run-based offense not predicated on heavy streaks/go routes... so dude isn't about to be out there expected to win deep routes constantly, nor is he expected to be the primary target and beat double teams.
Dude spent most of the SEA game running jet sweep type motion before plays and being a security blanket for JG - a role he could easily do again next year while Deebo continues the develop. And the more he does, the more Sanders has the chance for easy completions/yardage. Plus, playing for a winning team does a lot for a person. The fact that the team is so beat up and still doing so well honestly probably helps his likelihood to stay, because knowing how many pieces are missing and how they'd conceivably be back next season would definitely help.
Problem is going to be how much he asks for to stay and presumably be WR1. Kittle and Buckner need to be paid as priorities 1 and 1A. That being said, getting Coleman, McKinnon, Gould, Celek, Goodwin and a few others off the books could ease a lot of strain.
I do wonder, who might be available next year who could even fit the role needed? Deebo is heir-apparent, and while a Parker/Adams/Westbrook-type would be nice... a field-stretching type would be great just to run dagger concepts to spring Kittle open off a dig in the middle of the field where he is great at getting his yardage. Goodwin just doesn't have the size to be that person and expected to throw those blocks for counters and outside zone runs.
Would love to see a look where Kittle splits out wide, Jusz moves up off-tackle, Breida goes into the slot and Deebo is in the backfield. Just begs for mismatches everywhere, on top of good inline blocking if it's a run, and failing that, Deebo on a wheel route matched up against a WILL, Kittle running with a DB with safety help... Breida's gonna end up open on a slant. Dude pulls that ball down and with his speed, you can gash people. The personnel is coming along where every skill player is a hybrid type able to line up multiple places... just need that one additional WR.
(Man... getting Hardman or Watkins from KC would be best-case scenario I think. They're similar receivers so either works, but yeah. KC would try and gouge the team, unfortunately.)