Is it true that javax packages, in the Java language, are not stable and can be deprecated in future versions? In most of our project we use the swing packages which are included in javax.
This is nothing to worry about. There are Java classes that have been deprecated for the last 15 years but they're still in the core libraries for backwards compatibility.
Even if a whole swathe of javax.* classes get deprecated, they won't disappear.
You might want to take a look at Java 9's modular system too.