Dude, his codefendant pleaded guilty four months ago. He didn't engage in witness tampering (and this instance is a step beyond "Mom, what did you say to the cops?"), and was the less-involved party in the other crimes. Under the terms of the plea agreement, he's facing 5 years each for the two charges. And there's no federal parole system, so he's currently likely to spend most of those 5 years in prison. Manafort did more and has taken way longer. Even if he pleaded out today he would get a rougher deal.
The trial is in a month. Sentencing would be shortly after (EDVA moves fast) unless he flipped. That's not much credit for time served.