One approach would be to clone all your elements once you have added the classes that trigger the CSS transitions, then you can get the resulting properties from the cloned elements which will immediately hold the new values.
I suggest the use of a container element:
<div id="container">
<div id="one"></div>
<div id="two">
<div id="curr">current offsetTop of P:</div>
</div>
</div>
And with jQuery you would do:
$(function () {
//Kick off animations
$('#one').addClass('loaded');
//Clone container and position it outside of view
var $cloneContainer = $('#container').clone().css({
position: 'absolute',
left: '-99999px'
}).prependTo('body');
//Get offset from cloned element
var newOffset = $cloneContainer.find('#two').offset().top;
console.log(newOffset);
//Remove clone
$cloneContainer.remove();
});
Here's a working demo of this approach