Then what are the release announcements for?
As time passes, the Manjaro team continues to polish and improve the distribution, by adding new tools, changing default applications, and of course keeping all packages up-to-date. Those changes may then be featured in the latest ISO, so that new users start with a fresher installation.
How can i get those new features on an existing system?
All of these are among the packages available in the repositories; they are just a package installation or configuration reset away.
Because the user must stay in control of their system, these new defaults and packages are not installed during a system update, as not to overwrite the user’s customized configuration.