Google Now On Tap debuted with Android 6.0 Marshmallow last year at Google I/O. It was the next evolution for Google Now - with Google Assistant being the next step for Google Now with Android 7.0 Nougat. It essentially allowed users to go ahead and just long-press the home button on any screen and get information about what is appearing on that screen. It was a pretty cool feature to have included in Marshmallow, and is really helpful when you're looking for information about something, as you now longer had to jump into a new tab in the browser to search. Now it looks like Google is testing showing Google Now cards in Google Now On Tap, as a few users have reported seeing them appear already.
As you can see from the image above, the cards listed show items from Google Calendar (which are blurred out to protect the users privacy) as well as the weather for his area. Two of the more important and more useful cards from Google Now. There are likely others appearing as well, but those are what we can see in the screenshots that have surfaced. The user is also seeing some of the tiles that appeared in earlier leaks, for setting reminders, calendar events, timers and alarms. As well as shortcut for restaurants and such that are nearby.
It's tough to say whether this feature will be coming to everyone through the Google App (or at least those with Marshmallow since Google Now on Tap is only available with Marshmallow), or not. Seeing as Google routinely tests new features for apps and services like Google Now on Tap all of the time, but most of the time they never come to fruition. With Android 7.0 Nougat due to launch later this month, Google may roll this feature out with Nougat. As it is expected that many Google apps will see major updates with a new version of Android, which is actually quite common whenever Google releases a new version of Android. There's no word yet on when exactly Nougat will be rolling out, but it shouldn't be too long, since we have already received all of the developer previews.