The updates will be pushed out to the tablets over the next few weeks. If you don't want to wait, you can download the updates from the B&N website:
I have installed it and from what I can tell B&N is only adding apps; the fundamental Nook platform will not change. My Nook HD+ still has support for multiple user profiles, Nook Video, and other features.
But in terms of new stuff, I can see apps for Gmail, Chrome, Google Talk, Youtube, and Google Play Books.
Yes, B&N's tablets will now ship with a competitor's reading app. That is probably an unpleasant pill for B&N to swallow but I suspect that Google made it a requirement for getting Google Play on the Nook hardware.
So do you think this will be enough to rescue the Nook platform?
It could be enough, I think.
Remember, the problem with the Nook wasn't the quality of the hardware; the Nook HD and Nook HD+ are 7" and 9" tablets with excellent hardware and decent prices ($199 and $269, respectively). No, the biggest gripe I had was that B&N limited what you could do with a Nook tablet. That was why I returned my Nook Tablet in 2011, and it was a problem shared by the Nook HD and Nook HD+.
And I wasn't the only one to be chafed by the limitations. B&N's restrictions were also the reason that the various "Android on SD cards" did such a brisk business. I mean, Nook tablet owners were paying $30 or more just to escape B&N's restrictions. If that doesn't show that there was a problem then I don't know what does.
Update: I've just learned that the Nook HD+ still blocks me from sideloading apps. That is a poor decision on the part of B&N and it will to keep the Nook hardware less useful than the competition.