I use the code as follows:
$(\".reply\").popover({
content: \"Loading...\",
placement: \"bottom\"
});
$(\".reply\").popover(\"toggle\");
Yes you can, in fact the easiest way haven't been suggested yet.
Here's my way ->
var popover = $('#example').data('bs.popover');
popover.options.content = "YOUR NEW TEXT";
popover is an object if you want to know more about it, try to do console.log(popover) after you define it to see how you can use it after !
EDIT
As of Bootstrap 4 alpha 5, the data structure is a bit different. You'll need to use popover.config.content instead of popover.options.content
Thanks to @kfriend for the comment