Except with workarounds like for Java (which provides multiple packages for SE6, SE7 etc) there is currently no mechanism to provide versioned DocSets.

Given that in many frameworks, having multiple versions would be necessary (e.g. with Spring 3.x + 4.x, iOS 7.0, 7.1, 8.0 etc.) to switch when you're developing for different apps this would be a very exciting feature to have.

Would this be possible and in the interest of the developers,
and if yes, who of the users would be interested in this as well?

Thanks!