I'm not saying he is definitely gone, but when you lose your starting job, complain about it on social media, and the team you play for goes out and trades for a guy who plays the same position as you, there is a chance you are going to get cut or traded. And there have been media reports that it could happen. They may just decide to keep him around since they wouldn't save much money by getting rid of him, but if the right trade offer comes in or they get into a numbers crunch, I could see him getting cut.
I mean, I think Ridgeway is better than below average as a run stopping NT, but even if he is, that must mean they think Saunders is below that otherwise they would not have traded for him.
As far as the rookie, reports out of camp have been that Boyd looks great and that the team really likes him.
Beyond all that, Saunders has been a well below average DT since he got here and he's been a not insignificant part of why the run defense was bad last year.