For this requirement you can add a stTimeout handler with the timeout as per your requirment and re-initialize the dialog request to populate the saved values once the dynamic population of the drop down is complete.
You can use the below sample code:
setTimeout(function() {
$.ajax(Granite.author.DialogFrame.currentDialog.editable.path + ".infinity.json").done(handler);
}, 1000);
function handler(data) {
if any processing needs to be done, can be added here
});
}