NFL Media Insider Ian Rapoport says the Raiders are looking for a "superstar" coach who can not just win on the field, but in "every single aspect." There are roughly 25 other teams that would also like one of those, but you can't exactly pick them up at Rite Aid.
There's no particular reason to believe Gruden wants to leave broadcasting to coach the Raiders. It's even harder to imagine that Gruden would return to the organization if general manager Reggie McKenzie is in place. Rapoport says McKenzie's job is safe, which could limit the type of "superstar" coach the Raiders bring in. (There's one across town who could become available.)
In the meantime, the Raiders will turn to one of their many offensive coaches to take over, with offensive line coach Tony Sparano, senior offensive assistant Al Saunders and offensive coordinator Greg Olson all options to replace Allen. It would take a miracle for any of the names above to stick because Davis is looking for new blood.