I downloaded ckpackager from http://svn.ckeditor.com/CKEditor/trunk and ckeditor 4 sources from http://ckeditor.com/builder
I tried to minimize sources using this packager with ckeditor.pack file from CKEditor/trunk.
Then I removed some core/*.js which absent in this version. Packaging was completed successfully but I have js error in ckeditor.js (... new a.htmlParser.node() ...) Uncaught TypeError: undefined is not a function.
Is that happed because of bad ckeditor.pack? Where is I can find ckeditor.pack for ckeditor 4?
I got CKEditor 4 from https://github.com/ckeditor/ckeditor-dev and built it with CKBuilder which is in dev folder. Go by link for more instructions for russian speakers: http://habrahabr.ru/post/200952/