How else would you introduce backwards incompatible changes?
Especially with the LTS upgrade path that alasdairnicol mentioned I wonder what there is still to improve.
A platform that works hard to be backwards compatible does only additions and extensions, and keeps maintaining the old API as well so that old apps run without changes; possibly keeping around multiple depreciated ways to do the same thing (e.g. as win32 does).
It is debatable whether backwards compatibility is worth that cost (and it often isn't), but it's certainly a choice.
Then view HN threads of people saying they have thirty-million-line codebases which utterly rely on deprecated functionality and they never ever plan to upgrade or do even basic maintenance ever for any reason ever, and will abandon your platform and completely rewrite in something that treats them "better".
Not at all. That would have the added benefit of core developers thinking twice before introducing a new API - exactly like it happens with Linux syscalls.