Actually the announcement has been on the NCSoft launcher since 8/31/2012 - whether you decided to read it or not was your choice.
This launcher?
Now I will grant that once you click "City of Heroes" you get to see this:
But 1) the story isn't on the news page, 2) the feature they want us to see here is that Nature Affinity is available on the Paragon Market, 3) the other features they want to draw attention to are Amplifiers, Water Blast, and More Enhancement Trays.
If "we put the story on the launcher, it's not our fault if you didn't see it" was legally binding, we wouldn't have to click to confirm that we'd read the EULA when it changed. "Hey, we put a link to the EULA right there in the launcher, it's not our fault if you didn't see it and confirm that you read it," said no game company ever.
At any rate, the only way anyone can find out about the closure right now is by either logging into the game, or selecting City of Heroes in the launcher and looking very, very closely at what's in the lower right column. If someone isn't doing that (let's say, for example, they're on a business trip, vacation, working a ton of overtime, otherwise distracted and unable to log into the game right now), they have no way of knowing what's going on unless they frequent the forums or follow the CoH feeds on Twitter or Facebook.
Regardless of whether or not email address change over time, they'd still get better coverage by sending out email to every address they have on file.
Edit:
And, just for the record, I'm neither supporting nor attempting to dissuade anyone from considering legal action. I'm just pointing out flaws I see in an argument.