The list associated store's load
event is what you're looking for.
[EDIT]
As you point out in the comments the load
event is not guaranteed to be thrown after the items have actually been rendered.
I think your approach is correct, but instead of adding in place your functionality, why don't you fire a custom event at the end of the overridden method, passing the list item itself, so that you can listen for that event on the list?
Something like:
updateListItem: function(item, index, info) {
// function body ...
me.fireEvent('listitemupdate', [item, index]);
}
That should keep your code a little more clean and reusable.