Here’s what will happen. Mueller will say nothing new. Both sides will be upset. The left will insist that “nothing new” is something that needs to be investigated in depth.
Play, repeat, play repeat....
The left wanted another grandstanding circus where they could pontificate about all of Trumps transgressions and in this case try to validate it by leading Mueller into the fray, but they realized that in this case that the risks are potentially greater than the reward, because the whole can-of-worms about counter intelligence investigations against political candidates has not yet fully opened yet.
Nah.
Mueller will give the Democrats a few one-liners that Big Media will turn into anti Trump headlines.
Mueller will otherwise clam up and not answer the Republicans' important questions.
That is Mueller's track record and there is no reason to think he will change his behavior.