I think Mueller is going to indict all of those present at the Trump Tower meeting of June 9th

[Dr. Jack]

22. That would be something but I doubt it will be that extensive

Arresting the president's (i use that term loosely) son as his opening move would be beyond shocking. I'm not saying Mueller doesn't have the guts to do it but everything I have read about the man is that he methodically climbs the ladder, going after the lesser figures first and then builds a case for the higher ups. Shitbag Jr. is probably like the 3rd highest person on Mueller's list. Taking aim at him first thing seems unlikely. He needs to chip away at the outer walls before going after the rotten core.

My guess, and I of course say this without being a legal expert of any kind, would be Manafort, Flynn, and/or Flynn Jr. I have heard a good case for Flynn's son going down first. One of Mueller and Co's favorite tactics, from what I have read, is to go after the family members of lower level people in these crime syndicates to make said lower level people much more like likely to cooperate to save their and their horrible offspring's necks.

Then again, its all just speculation. Fun speculation, I have to admit but still, we are going to have to wait and see.