Imagine they skip 12 and call it 13 like they did with W10

With as little sense as Microsoft makes most of the time, that decision actually does make sense. A lot of programs and scripts were lazy about checking the Windows version and just checked for the presence of a '9' in the version string to determine if they were running on Windows 95/98.

A bunch of shit would have broken if they had released Windows 10 as Windows 9, which is what it should have been semantically.