That, and keep releasing new versions that are lower-numbered.
You can't abandon KDE 3.5 and then say that people shouldn't have migrated to 4. The current version is whatever keeps getting bugfixes.
Most serious software packages don't just do all bugfixing at the bleeding edge. Heck, the kernel still has full support for v3.0 and v3.4, with later versions not having longer-term promises (they're the equivalent of KDE 4 or 3.99.9 or whatever).