code: function() {
          var wrap = arguments[0],
              items = this.getLayoutItems(),
              index = Ext.Array.indexOf(items, this.activeItem);
              
          return items[index + 1] || (wrap ? items[0] : false);
      }
docs: Return the active (visible) component in the layout to the next card
  @returns {Ext.Component} The next component or false.