GRob is a $6.77 mil cap cost. And since it is all guaranteed, then it is a full $6.77 million dead cap space if they release him.
Barring a complete meltdown and a bad attitude, it is highly unlikely he will be released.
Cap hits do matter and this is a pretty big one. If they feel they can keep him and get something from him, they will.
But, I suppose, if he is bad enough that under no circumstances can they trust him on the field not to make the same mental mistakes he's made for 4 years, they may have to do it and suffer for it.
Clearly, GRob cannot do the mental part. And if can't after 4 years, he never will.