We should have caught the change, as it has been rumored for months now, but alas we have been playing with shiny, new tablets lately. The change in 2.11.670 is rather straightforward: how the messages appear in the notification center.
Previously, notifications for new messages would be formatted this way: Sender: Message
Relatively direct, but one line dedicated to a WhatsApp message is rather limiting. Instead, the new format has it as such:
Now, the person who sent it is on its own line, with text in bold. Meanwhile, the message itself gets a little breathing room on a second line.
Interestingly, notifications in Windows 10 are also formatted this way. WhatsApp appears to be getting ahead of Microsoft's changes in preparing WhatsApp for the new OS. Indeed, in Windows 10, you will be able to dismiss individual notifications within services, as opposed to the 'all or nothing' style that is currently found on Windows Phone 8.1. We are also hoping that users will be able to respond to new WhatsApp messages directly like they can for text and Skype messages.
For what it is worth, the private beta of WhatsApp is still floating around, being updated on a regular basis. However, its version number 2.11.670 now matches that of the official release, meaning the two have once again caught up with each other. Presumably, WhatsApp will now start pushing smaller updates to the beta channel again for the next few months before they go to the public one. We'll keep you posted on any changes we find when that starts to happen.
Big thanks to Henock S. for the screenshots!