To be a successful cross-platform development environment, there would have to be lots of these. To my knowledge, only web apps are that widespread and used by the general public, not primarily for in-house apps.
So although end consumers might not see them, it will certainly take a long time for SWT or Swing to die. These are the same class of applications that are keeping IE 6 alive, after all.
Does this matter to Apple? I doubt it's significant, as most of these applications are probably running on Windows desktops already. Probably more significant is the legion of Java developers that have been vocal proponents of Macs over recent years. The numbers of such developers might not be so great in an absolute sense, but the amount of noise they create is disproportionate. And, more importantly, they are more motivated to build interesting stuff for the platform they use.