If new content was designed to patch old content, it would be clearly labeled as such. But it's not. It's pretty ludicrous to say that the Core rules don't stop at the last page of the Core Rulebook.
Also, how is a player/GM supposed to know which pieces of content are "patches" and which are not? How can a "patch" be effective if we don't even know what the "patches" are?
Maybe not patch but natural evolution or upgrade. It doesn't invalidate the old class but gives you options to use the new classes over the old class. The rogue is perfect example, a weak class but the ACG has the Slayer and the Investigator to replace the rogue with that do the rogues job much better. You can still use the rogue though but why would you if you had the ACG?