The contract in this case is that there will always be a version number, and anyone who expects it not to change is an idiot or just being obtuse.

> anyone who expects it not to change is an idiot or just being obtuse

If this was the case, Microsoft would have never had to skip from Windows 8 to Windows 10 (see below in another comment: "starts with Windows 9" was used in the wild to detect Windows 95/98).

> anyone who expects it not to change

And you appear to be using an example of a version-change curiosity as a counterexample. It is not a counterexample, because the version number in question changed from 8 to 10. In my original formulation, anyone who claimed to worry that the number would stay 8 forever was being an idiot or being obtuse.

I think that holds up. It was not part of my comment, but someone who expected it to be 9 would not be an idiot or obtuse, because that would have been a reasonable guess, absent additional information. They were expecting it to change but were surprised by an exceptional circumstance.

But this is getting a bit silly; there may be someone out there who thinks version numbers should be immutable across versions, but I bet they're pretty lonely. It was an example picked up while making a wider point.