Is JavaFX replacing Swing as Javas client UI library?
No. JavaFX is a rich client platform for building expressive RIA for multiple screens such as the desktop, browser, mobile and TV. Whereas Swing is a set of extensible GUI components that enable developers to more rapidly develop powerful Java front ends for desktop-based commercial applications. JavaFX applications that are designed for desktop environments can take advantage of the powerful Swing widget toolkit to build RIA that are optimized for the desktop.