He Dies Trying to Fix the Bridge
It feels pretty obvious that Rick's end will somehow be tied up with the bridge he's so obsessed with fixing. It's the figurative and literal means by which he can do right by Carl's dying wish. With the bridge repaired, all the communities will be easily accessible to one another, which will make trading easier and thus a more stable existence for all. But as we all know, no one else is here for that nonsense. It would only be fitting that Rick dies on that bridge — whether amid a walker-horde attack or while trying to patch it up. His death will inspire everyone else to pull their sh*t together and reach some sort of accord, since they have bigger threats on the horizon.