While there has never been a female General Manager in the history of the NHL, Madigan is more than qualified, and given how well the Devils have built their current team, the belief is that this would be a huge loss to the organization if she were to depart.
However, that's a distinct possiiblity, as she has one of the brightest minds in hockey, and if she is given a role and given the freedom to build things the way she wants in New York, confidence is high that they could finally go into the rebuild and push to build something better than what we've seen in recent years.
Ultimately, Madigan is likely to be one of many candidates to replace Lou Lamoriello as the person in charge of the Islanders, so while she may not eventually end up getting this role, the belief around the NHL is that in due time, she'll find herself as the General Manager of a team in the league.