Sure... pause is a good solusion, but don't work then I use tweenTo(copy)...
Both boxes animated.
http://codepen.io/dkdf/pen/qDkob
var tl = new TimelineMax({paused: true});
tl.to("#redBox", 1, {left:500});
tl.addLabel("preload_and_change");
tl.add(function() {
tl.pause();
});
tl.to("#blueBox", 1, {left:500});
tl.addLabel("step2");
tl.tweenTo('step2');