I read that at Wikipedia. TLK has already produced as a Platinum Edition in October 2003. Only for a short Time.
But 2011 will be produced as TLK Diamond Edition, with many specials and probably all three parts of Blue-Ray and DVD. But this will only be offered for a short time. So if it's there, you should buy, otherwise you have to wait several years until it comes back. This principle is called from Disney "Disney safe".
Here is the link to the german Wikipedia, the english version is not so good for this article:
http://de.wikipedia.org/wiki/Walt_Disne ... um_Edition