Sean Monahan loved his time with the Canadiens. It's fortunate that everyone in the organization and among the fans loved him too. When the general manager is almost afraid to announce the trade to his head coach because he knows it will greatly disappoint him, it says a lot.
Indeed, Martin St-Louis was a fan of Monahan and would have certainly liked to keep him. It could well be postponed in his case, as several signs indicate that signing him in July is far from impossible.
In my opinion, it all depends on his playoff journey with the Jets. Like any athlete, the goal is to win major honors, and the Stanley Cup is the toughest trophy to win in professional sports.
However, the Canadiens won't be contenders for years. Monahan will still be good for several seasons, but let's be realistic, his injury history works against him regarding his longevity in the NHL.