Sorry, late answer.
Yes, of course:
in a terminal:
emacs -Q

Then, in emacs :
- M-x newsticker-show-news
- in "Virtual Feed", click on "All items"
- click on "Date"

You can check that the sorting is supposed to work, by doing the same manipulation on Emacs Wiki :
- in "Feed", click on "emacs wiki"
- click on "Date"

As you can see, the news are sorted, and not gone, like in "All items" after click on "Date" button.