Drouin could return to the team and play for the remainder of his contract. His $5.5 million AAV expires in two years, making him a UFA. Drouin also submitted a list of three teams he did not want traded to in the last two years.
Drouin could also return to the Canadiens in September, play a little, and show what he can do to maximise his market value before being traded. I'd assume only if he wants to be traded and Bergevin can get him a good price.
We don't know what Drouin was or is going through, but if it's related to the pressure and all that comes with a big hockey market, he might ask to be traded.