If any top-level person (BHO, HRC, etc) is getting arrested in all this, then Sessions cannot be the one to pull the trigger (or if he does it has to be completely deniable – maybe this is the true purpose of Mueller). The political shitstorm that would erupt for Sessions to do it directly would be the biggest shitstorm in the history of shit.
How long can you be arrested by the feds before they have to announce? Probably there is a nat sec exception too. When that clock runs out on this ATL extract, the show is on for sure. Enough time to pass tax cuts first?