This kinda sucks, although it's hardly unexpected. Google squelched their Buzz. They collapsed their Wave. They closed the book on Reader. And now they're negating G+.
Of course, many of the goodies live on. Wave is where Google was playing around with multiple concurrent humans editing the same physical document and keeping them all in sync. That's now found its way throughout Google Docs. Similarly, G+ had the best photo handling out there, and that's been spun out into Google Photos. G+ was the first social network to support both controlled sharing
and unlimited public dissemination, when Facebook had a limit on the number of friends and Twitter had (well, still has) only fully public sharing. Facebook moved quickly to close all those gaps and Google? Gave up.
Still, to pick one example, if you're an Android Wear developer, Google had a G+ Community as the primary place for announcements and discussion. No word on a replacement. G+ also served as an easy way to set up a closed beta for an Android app, where you could connect the beta list again to a G+ Community. I'm sure there will be some other way.
I'd been posting pretty much everything "personal" to both sites, whereas I only post "professional" things on Twitter. I do have a much narrower set of friends on Facebook with whom I share things about my kid. (Would have done the kid stuff elsewhere, but Facebook is where the audience was.)
So... maybe one of the random other social thingies (Mastodon?) will find a way to step in and build something. Most likely though, there won't be a replacement. It's just going to die.
At least we'll still have YouTube comments! Oy.