Well, Google Stream would be a fine name, right? But maybe it's just Google+ in the end. Fact is, Photos will be an independent occurrence. Hangouts on the other hand, is already separated and never really was seen as part of Google+. Only a feature was integrated into Google's social site, making it possible to chat while using the site.
Photos however is the main focus. While Google+ is popular among professional photographers, the service connection to Google+ made some people uncertain to trust this place to archive private photos. It's kind of scary for many. Now with a standalone Google Photos app and rebranding, the way is set for people that don't want to do anything on Google+, to use it as one of the greatest places to store, enhance and share photos on the web.
Obviously Auto Backup photos and albums will be stored in Google Drive which would be a logical and good choice. Drive on the web could use the album frontend that now Google+ is using with a slight different design to integrate with. But that has to be seen.
Another question rises if space taken by the photos will be free like with Google+ Photos. All photos which equal or less than 2048 pixel per side, did not count towards your available space. So you had unlimited storage for such photos. Now rumors are that Google eventually lifted the 2048 pixel limit and give unlimited storage for all photos. Amazon offers unlimited cloud space for photos with it's Amazon Prime service, and Flickr giving 1 Terabyte for free, which is enough for most private users.
Google Stream (or Google+) could then be without too many changes just be what it is now. You can share easily with one click from Photos like it was before. Photos from drive can already be included if checked in the settings, and it could be that there is not a change in the user experience. However it could be a remake of Google+ which is unlikely. Rebranding in "Google Stream" is not really necessary.
So I can't exactly understand why some sites are again (like so many times) foretells us the end of Google+. I'll guess they just want a sensation and want to see Google fail again. Really sensationalist. If you lean back and look on your phone, there is Photos, Google+ and Hangouts already as separate occurrences. Now they make Photos, like the Hangouts app, really independent, and possible to use it without even knowing about Google+. That's all.
It's exciting, I see that, because it can attract many more users that want to store their photos without using Google+ at all. And the ones who do, still have all features available.
What exactly is happening, we will see this week, or next, or in May. But nope, no #pluscalypse on sight.
Animated G+ logo by Jakob Rode Gellett