The rumor is/was that when Trump met with Mueller (and Rosenstein) at the White House before the mule became OSC it was said that when it came to former presidents, they should not be prosecuted (unindicted co-conspirator?). So, yes, Obama & Bill are on the table but spared the fire. HRC however ... TBD ;)
The reason Obama is untouchable is because he is not a natural born citizen and they ALL knew it and went along with the Kenyanesian Usurpation.
Everyone in the District of Corruption (except Trump) is complicit in the violation of the Constitution.