Amgine:
There is no reason WMF press releases could not be be protected as original source documents on en.Wikinews, as a part of the archive policy on that edition.
I would prefer not to do this. We frequently do report about Wikimedia projects; if we additionally host press release, this will cast a shadow of doubt on the neutrality of our other articles.
We've had stories like: http://en.wikinews.org/wiki/Wikimedia_Foundation_and_Answers.com_announce_pa...
This was short and shallow, but it still linked to an ongoing community discussion, which a press release almost certainly would not. Even in Wikimedia controversies, Wikinews has a responsibility to report the facts fairly and neutrally. Press releases would affect the perception, if not the goal.
Erik