You're probably right.
There are three likely scenarios here. Mueller can cut his losses and close the investigation with the prosecution of some poor schlemiel as a face-saving gesture. He can leverage a low level indictment into snatching a bigger fish perhaps all the way to Trump. The most likely outcome, he will simply drag this out through every election Trump will face including mid-terms to be used as campaign talking points for Democrats.
How Mueller is above being himself indicted is beyond my comprehension.