Since TinyMCE extension is just PHP wrapper for some JS code, I suppose it’s not so hard to modify a couple of lines of the extension’s code to make it support 4.x.
I never use an yii extensions which is only a wrapper for a js one, I prefer to download the js and write a wrapper.
Usually a wrapper result in 10 lines of php code, it absolutely does not worth the pain of looking for a yii library which may lack of some parameter I need.