Re: A new scheme?
'Cos that's just plain silly willy-waving.
Version numbers are meaningful in a few ways:
Compatibility breaks. There are always lines where forward, backward and interoperability compatibility can't be maintained.
Feature checks. Features get added, replaced and removed.
Downgrade. It might not be practical to downgrade back to the previously-installed afterwards.
Upgrade stages. It might not be possible to support upgrading from all prior versions.
It is very useful to signal these barriers in the version number, or to at least make it easier to document - "Compatible with 3.x and 4.x" etc.
- Marketing tends to ruin all the above of course, commonly with either "big numbers are good" willy-waving, or by requiring particular numbers for particular features. "Can't call that v2, we promised feature Y would be in v2!"