As noted a few weeks ago, Humana has already decided that regardless of what actions Donald Trump, Tom Price or Congressional Republicans end up doing (or not doing), they expect the 2018 individual market to be a big mess they want no part of...either on or off the exchanges:
...based on its initial analysis of data associated with the company’s healthcare exchange membership following the 2017 open enrollment period, Humana is seeing further signs of an unbalanced risk pool. Therefore, the company has decided that it cannot continue to offer this coverage for 2018. Through the remainder of 2017, Humana remains committed to serving its current members across 11 states where it offers Individual Commercial products. And, as it has done in the past, Humana will work closely with its state partners as it navigates this process.
Again, it's important to stress that Humana isn't just bailing on exchange participation, but to the best of my knowledge, they're pulling up stakes off-excahnge as well.