What is the disadvantage of using
GUIKit now? What does it mean that it is being deprecated? Will it be removed from Mathematica in some later versions?
It is an indication that
- It is no longer under active development (or, really, any). Bug reports may be ignored unless they have severe impact (like security issues).
- You should try to port existing code to a new framework, namely built interfaces.
- It will not be ported along with the rest of the product to new platforms.
- It may in the future be dropped from the product. But that is not imminent.