I don't think there has been anything that hasn't appeared on old maps in new chunks
This has been my experience too. It would seem silly that Mojang would create new features in Minecraft and not make them compatible with others. There is a process to this, you know. If you are having problems with maps in regards to chunk updates and new features, I would chalk it up to a bug that's the exception rather than the rule. Checking the changelogs and bug lists to see if others are having similar problems would always be recommended.