Update - December 10, 2018
After discovering another security issue potentially impacting 52.5 million users, Google today announced that the consumer version of Google+ will be shutting down four months sooner: in April 2019 instead of August 2019. Furthermore, Google will shut down all Google+ APIs within the next 90 days. “While we recognize there are implications for developers, we want to ensure the protection of our users,” said David Thacker, G suite vice president of product.
We plan to continue supporting Google+ after the April deadline, although we might scale down its features to align to the social network's popularity and our members plans going forward.
More on the Google blog here.