Teams without turmoil are rarely looking for a HC. Also, organizations which undergo ownership change always have turmoil. Always. That said, I think you overstate the "turmoil" a bit.
As for Pegula's plan, I am quite sure he has one but is not likely to share much with us. He previously said his plan was to hire a consultant after the season to help him evaluate the organization. I suspect he was not thinking of blowing anything up given the 9/7 finish, but looking for independent advice on structure and personnel on the management side. Marrone quitting has put that on hold. The priority has to be the HC. Stay tuned in the rest.
As for the QB quitting, I must have missed the outpouring of tears and consternation around here that Orton would not be back. I think most people had already concluded an upgrade was needed. Nothing has changed. The Bills needed a QB before Orton retired.