Renegotiated with the Ravens to stay: http://espn.go.com/nfl/story/_/id/8336809/bryant-mckinnie-restructures-baltimore-ravens-pact
I don't quite understand how this works. I've read at multiple places that a player with 4 or less years of experience get waived. Anyone with more experience than that gets released/cut. But when Vikings decided to let go of Moss in 2010, he had almost 10 years of NFL experience. He was waived, not released, and consequently, claimed by Titans. This is a dead case anyways as McKinnie got negotiated anyways.
It's not a rule, it's a consideration. I'm sure you know but if you get waived you go through the waiver process and get claimed by any team that wants you. At that point you sign with them or sit out. If you get released you get to pick your team. If you are a vet a team will be nice and release you unless that hate your guts (see Moss).
I think there is a rule about it. Why would teams care if a player goes on waivers or gets released? In fact, teams probably prefer players to be released as they can sign them to their practice squad. But teams can't always release players (see the Giants TE claimed by Pats). So it is a rule that isn't entirely dependent on years in NFL.