Generally speaking, any official word on SR5 does appear on shadowruntabletop.com/blog. It just doesn't always appear there first, but it does appear there.
But I also make a pretty good effort when I have time to ensure that anything official related to Shadowrun, whichever property, is posted to the tumblr. When they let me start the Shadowrun tumblr, they gave me dispensation to post whatever I want so long as I don't break my NDA. Given the whole Year of Shadowrun, I've also been covering all of the properties—SR Returns, Online, Sprawl Gangers, Crossfire, etc.—however I see fit. Plus the constant positive coverage of SR:R helps draw traffic to the tumblr from people who can then get into the game. But that's all at my discretion. It helps that there's also now an official CGL tumblr.
For the most part, you don't have to worry about it. If it's not on shadowruntabletop.com/blog or shadowrun.tumblr.com it's not official and it's almost certainly discretionary like references to the development process for different products and while it's official insofar as it is something stated by an official representative of CGL, it's not "for official release" like street date announcements.
As it happens, what I know that has been mentioned publicly somewhere or another is that there are movements on the Intro Box Set, on a box set for BT that I forgot they're also doing, Crossfire, and a couple of products like Run & Gun.
Then there's also stuff that hasn't been mentioned. There's the stuff that can be inferred as in-progress but where official word has been silent of late like the errata/FAQ, Sprawl Gangers, the novels/fiction, and ebooks ranging from enhanced fiction to the Shadows in Focus series that I guess is official now that it's been mentioned in the Jackpoint page for Coyotes and Gun Heaven 3.
There's stuff that hasn't been mentioned officially but can be inferred from common sense: core supplements.
There's the stuff that's known to CGL and its partners and to freelancers that we can't mention.
And finally there's stuff that's only known in-house at CGL (which basically means Randall, Jason, and maybe a few other people).
Even the stuff I post about on the tumblr can end up not happening or change (maybe significantly). Just the fact that sell sheets for retailers can differ from what is final is further proof that is how it is.
Which is all a long way of saying that there are many reasons why they don't make major announcements until pretty much they are certain that a product will be sold. If it's not on shadowruntabletop.com/blog it's just not that important for you all to know because there's nothing you can do about it anyway. If it is, it generally means that you can buy it. And that's that. It is a business after all.
