Do you not think there are more people and companies involved and those said companies have a say so in this matter as well?
Keeping DD on board allows for all the things from both UTAD and Gruden to get worked out and that does not mean announcing DD's termination with 2 games left in the season. An official search has to be started and that will not happen till after KY but if you know you have your guy, speeding up things only looks bad on UT and Gruden.
I would also think ESPN and their deep pockets will have a say so as to when this news can be released since they are going to have to negotiate a new contract with MNF sponsors and find the guy they will want to promote to replace Jon.