Chip Towers' thinks (h/t Blutarsky) Grantham could end the speculation by saying one word. However, I'd say that there are very good reasons for him to not say anything. One could be he is in the mix, but Kelly, understanding the importance of NSD and not wanting to harm a relationship with a school, is holding off until after NSD to talk to Grantham. Another could be Grantham has told Kelly he isn't interested in talking until after NSD. Another could be Grantham has told Kelly he isn't interested in talking at all, but is letting the speculation sit out there because it is good for Georgia's recruiting to have a possible future NFL DC on staff.
Of course, he could be wary of making statements that others will use later to accuse him of lying, cheating and whatnot, should he actually decide to go to the league. Note, all of this could be said for Kirby Smart.
I know there is broad speculation about a number of candidates, but the one that seems most likely to me would be a current position coach that Kelly has already worked with who is also coaching in the Super Bowl. That is Ed Donatell.
As I said in a prior comment, I have no doubt Grantham will do ok if he goes to Philly. I just doubt he is Kelly's first choice.