1) Creating a more immersive campaign world that feels richer because it is larger than the PCs' own experience.
2) Teach the players about the world, its particular lexicon, history, culture and so on.
3) Seed upcoming events they will get involved in.
4) Seed possible events they might want to get involved in.
And 5) Ultimately, create excitement by having the characters' own exploits referenced in an article.
Possibly 6) Allowing the players themselves to use the news service in-game to transmit information, influence opinion or fill their needs.
For an open-ended campaign, #4 is, I think, most important. Here you can put all sorts of ideas you've had and would be willing to expand on, but you're letting your players actively choose to pursue them. It was your idea all along, but now they've got skin in the game. On a narrative level (and you know how much of a "narrativist" I am), it gives the characters more agency, as opposed to having things happen TO them, or as in computer game RPGs, requiring a third party to consistently give them things to do. #3 is just as useful, of course, but used to create a sense of foreboding, tension, or inevitability. Here, you should try to build your coming event up over several releases (issues/updates), a developing story that eventually comes to a head.
Mocking up a newsletter is a bit of hard work (which is why I adapted mine from one found online, so thank you Mimir.net - a great resource for this particular campaign world, folks!), but a website or Facebook group can serve just as well, and be a whole lot more practical. These platforms can even let your players get in on the game. For example, in my Dream Park campaign, players took on the roles of maverick LARPers who themselves took on roles in holodeck-type adventures for a larger public. The website kept their standings up to date, showed all options open to them and advertized upcoming "events". But we also had a dedicated mailing list where players would share their favorite moments, but also, in-character trash talking, fake eBay auctions of props used in the game, and "reviews" of their performances according to the in-world media.
It all depends on the world you're trying to build. A Supers world might have a website of Who's Who entries for heroes and villains (and upcoming villains) and issue synopses of the characters' own "comic". A modern supernatural game might have an encrypted website filled with secret files filled with rumors and arcane information, accessible via smart phone during the game; is the right solution somehow in there? So many possibilities. And for adult gaming groups that don't get together very often, it may be the perfect idea to keep participants interested, and fill those long gaming gaps with in-world activity.