There is always an example that will support either sticking with JB as a smart idea, as well as an example of moving on from JB, as a smart idea. Fans tend to use whatever example supports which choice they personally want. Folks tend to cite the current situation with the Steelers as evidence that moving on is a good idea, yet ignore how moving on has served the Browns. There is no one answer fits all.
In this, I bow to the braintrust of Reich/Ballard. Frank was a very astute QB, knows what the position takes, and I feel he has a good pulse of what Jacoby brings to the table, both on the field and off, as well as preparation, meetings, practices and so on. I have seen Jacoby look like the guy that could become the long term QB for the Colts, and I have seen him look like a QB that has too low of a ceiling. How much of that is circumstance, is the proof in the pudding.
That said, I believe that the upcoming draft and FA opportunities for the Colts are really important, but every year is really important. I don't think this offseason "defines" Ballard's legacy any more than every year does. They're all extremely important.