I noticed that too.
Rudy and Mueller are in periodic negotiations, so there is some sense (maybe a mistaken sense, but a sense) that Trump will be personally clear of Mueller by the end of the year.
A full exoneration well before the midterms is required to prevent the investigation from being just another Democratic dirty trick designed to sway the 2018 mid-terms.
Successful dirty tricks resulting in Team Donkey gaining control of the House means VSGPDJT is very likely to be impeached.
So, end of the year just isn't good enough, in my opinion.