PlayerChangedWorldEvent#getFrom is the same as PlayerChangedWorldEvent#getPlayer#getWorld, wheras previous behaviour was not so.
I have attached a plugin in which listens to PlayerChangedWorldEvent:

@EventHandler
public void onPlayerChangeWorld(final PlayerChangedWorldEvent event) {
 getLogger().log(Level.INFO, "From: " + event.getFrom().getName());
 getLogger().log(Level.INFO, "Current: " + event.getPlayer().getWorld().getName());
}

The expected output of "from" should be that of the origin world.