This will never, never happen. Marrone is a former OC and has hand-selected Hackett. Firing Hackett and hiring Kubiak would indicate:
1) Marrone exercised poor judgement in regards to hiring Hackett.
And
2) Marrone is not a good enough offensive mind and leader to right-the-ship by either (a) mentoring Hackett better or (b) assuming offensive control of the team himself.
In effect, the only way we are hiring Kubiak is if Marrone is fired himself.
Besides, I don't know what happened to Matt Schuab. At one point, before this season, he was an excellent QB. The type of QB, on the right team, could probably get you deep into the post-season.