Will she make the Oct 15 debates? Hillary joining the race is like adding a 4th ring to a 3-ring circus, like lobbing a poop grenade into a pile of manure...
She’ll probably officially announce on Halloween.
She won't bother with the debates. She'll lay low and work behind the scenes to take out the front runners. Bernie is done, so she doesn't even need to do anything there. Biden is slipping fast, so it's just a matter of giving him one final push over the cliff. Don't be surprised if some major problem for the Warren campaign suddenly surfaces. When it does, Hillary can come riding to the rescue "for the good of the country, and the party."
The democrat campaign for 2020 is simply lie about Trump. Who is best at lying about Trump? Hillary, by acclamation.
With one more zombie on the stage who would notice?