Just so long as you have Google Now activated on your Android device, you'll be seeing "G" notifications soon. The notifications you're getting might not end up being all that different from what you've been seeing before today, but they will LOOK a little different. The biggest change is the branding. Instead of just a circle with an icon in it, your notifications from Google Now will also have the newest version of Google's "G" logo.
What does this mean for you and your Android life? It means you're going to be a lot more aware of the fact that you're using a Google device. The change might seem slight to some, and it really doesn't affect usability in any way at all, really, but Google's intent is clear.
If you're using an Android device that's licensed with Google, they want you to know about it. They want to make clear that, when you're getting a sports score update from Google Now, you know you're getting that score from a Google-branded app environment.
For those of you looking to get your device prepared for the coming of the "G" - you're out of luck. All you're going to be able to do is make sure your Google app is updated as much as possible. You can find that Google app on the Google Play app store.
This change is coming to users in waves, and its all server-side - as confirmed by our own devices and several helpful readers.
So all you can really do is sit there and cry, or get pumped up for the brand!