Let's wait for the end of the season to make a decision. I get the disappointment about the seeming lack of improvement or even decline in the program under Holgorsen, but a mid-season firing for nothing more than poor coaching is not going to help this team this year or put us in any better position for the future if we do make a change. Unless you have some major wrongdoing (showing up drunk like Sark, or getting caught cheating, etc.) there is really no good reason to let a coach go in the middle of the season and a lot of good reasons to let him finish.
First, however unlikely, the coach could get it together and finish surprisingly strong. The chances of a team rebounding under an interim coach are lower because the message has been sent that the towel is being thrown in. Even if you had a guy on the staff (which I don't believe we do) who is a strong candidate for the permanent job you would be more likely to undermine the goodwill toward him than build support for him. If the team does finish poorly the interim coach will probably be unfairly be held more responsible for it than he should be and he won't be able to really put his imprint on the team and show what he can do with a full offseason of preparation. It's kind of starting behind the eight ball to take a team over mid-season.
When you don't have a viable candidate for the permanent job on the staff, you don't gain any advantage in terms of bringing in a new coach from outside the program. We can't hire anyone until after the season and neither can any other school that we might be competing with for a particular coach. We can though make quiet, private inquiries and get the ball rolling without disrupting this season.
Let it play out. We might disagree among ourselves as to what is good enough this year to warrant keeping Holgorsen but give him a chance to meet whatever standard you think should be met. The reality that in today's environment there will be pressure to either give him an extension now or fire him is definitely not going to be in his favor unless we finish so strongly that someone could objectively say a longer term commitment doesn't look like as bad an idea now as it looked when Luck gave him the extension. It would be easier to keep him if we didn't have to worry that keeping him but not extending his contract would negatively impact recruiting, but that's just the way it is.
Personally, I'd be on the fence if we finish 5-4 in the conference and it would depend on how we look going 5-4. Better than that and I think we should extend and hope for the best. Worse than that and I think we need to move on because there will really be no plausible case we are improving.
I never bought into Luck's proclamation that we were ready to compete consistently for national championships and all we needed was the right coach, so I don't think the fact we are nowhere near that level is grounds for firing him. It's not Dana's fault Luck often spoke and acted rashly and created (or at least exacerbated) unrealistic expectations. I do think that by year 5 we need to see real improvement not excuses for why it's so hard to improve.