I don't really expect to hear anything until Sunday at the earliest at this point, and more realistically, not until Monday.
Sunday's early game is on Fox, with plenty of leadup, and I could imagine Fox has either begged him to keep it quiet until the broadcast and announce it there in a designated segment, or a day after so it doesn't interrupt planned coverage. Any Saturday announcement makes everyone on the broadcasting team have to scramble (my buddy works for Fox's main NFL broadcasting, so I have a solid idea of how locked in this stuff tends to be). Hell, he could also have space there to announce he's coming back to Fox.
Not that a leak would shock me, either.