Kindle4PC was updated on 3/16/2012 to version 1.9.2 (38420) available here:
That one did have support for new features:
1. Localized app language in French, Spanish, Italian, and Brazilian Portuguese
Support for collections allows you to take control of your Kindle library and organize your books with ease
2. Book Extras by Shelfari. Access character descriptions, important places, popular quotations, themes, and book-specific glossaries from Shelfari, the community-powered encyclopedia for book-lovers
3. Support for Kindle Print Replica content, which look like the corresponding print book with words and images in the position corresponding to the print edition. See more detail on Print Replica content here.
4. Support for reading most PDF files within the Kindle application, including functionality such as zoom and pan, highlighting, note taking, dictionary lookup, and bookmarks