The init and createControl callbacks are no longer called for the Plugin object.
Secondly, you need to call the addButton function on the Editor object.
A proposed solution could work like this (taking code from your post above):
(function() {
tinymce.create('tinymce.plugins.ShortcodeMce', function (editor, url) {
tinymce.plugins.ShortcodeMce.theurl = url;
var btn = editor.addButton('symple_button', {
type: "splitbutton",
title: "Insert Shortcode",
image: tinymce.plugins.ShortcodeMce.theurl +"/shortcodes.png",
icons: false,
menu: [
{ title: "Shortcodes", classes: "mceMenuItemTitle", disabled: true }
]
});
Here's the reference of the Button interface in TinyMCE API 4.x: http://www.tinymce.com/wiki.php/api4:class.tinymce.ui.Button