In reply to Phillip Hawley.

In my experience WordPress is excellent at maintaining backwards compatibility.

It's the theme and plugin developers that neglect their themes and plugins that are to blame for any issues you may encounter with plugins or themes when a new version of WordPress is released.

I'm coming at this from the perspective of running a company that produces one of the most popular commercial WordPress plugins there is. WordPress does an excellent job of changing things in such a way that backwards compatibility is maintained. Almost to a fault in some cases.

There are situations, major updates to jQuery for instance, that most definitely will require plugin and theme updates. But this is completely unavoidable and it's exactly why theme and plugin developers must maintain the themes and plugins they make publicly available.

WordPress development isn't done in private. What they plan on doing is publicly known. It also goes through a long beta process and release candidate process before being publicly released. This is when plugin and theme developers need to be testing their themes and plugins to ensure they function properly with the new release.

If you have plugins and themes that are constantly breaking when WordPress releases an update then you should probably revisit which plugins and themes you are using. It sounds like they aren't being maintained properly by their developers.