Shanahan has to be next. You can only get rid of so many underlings to mask your ineffectiveness and failure of both vision and implementation of the same, before it is apparent that the problem resides at the top. Shanahan sets the vision, goals and culture of the hockey organization.
No matter how it is sliced, despite some of the workplace improvements he has implemented, ultimately team president is responsible for bringing in the personnel, both from a GM, scouting, coaching and player perspective. Even though he has the GM doing a lot of the heavy lifting for decisions, it is his vision and goal setting that drives the organization forward.
I think from a performance perspective, he has to be next, otherwise, Keefe leaving is just window dressing. Just like Dubas leaving is window dressing to some degree. The problem is, unless Shanahan can do some self-reflection and evaluation and submit his own resignation (fat chance of that), Pelley is going to have to make that hard decision. You can put whatever coach in place - the same culture and the same players aren't going to produce a different result. I think we have seen that already over the years during Shanahan's tenure.
All that said, while I am not a fan of Keefe, I do hope he lands somewhere and hopefully has some success in a different environment.