A pinch-to-zoom trackpad and a "Peeking Launcher" are set to arrive on Chromebooks sometime in the future as part of an update to Chrome OS. These changes to the operating system are coming alongside a number of others which have recently been discovered as being currently in development, and a number of others which have been talked about numerous times, such as Google Assistant, which is also due to get its own physical key on the keyboard of future Chromebook models.
The pinch-to-zoom feature for the trackpad is reported to be in development for just a handful of Chromebooks at the moment, albeit without any sort of confirmation as to how long it will be before the feature is rolled out to them. This doesn't mean that it won't be developed for other Chromebook models, but for the time being it seems that it may be just for the one's listed, which are the Samsung Chromebook Plus and Chromebook Pro, the 2015 Chromebook Pixel, and the Chromebook which is codenamed Eve, a Chromebook which has also yet to release and receive a formal name. This is all according to a recent commit that was found over on the Chromium repository, and the current suspicion is that it may arrive with Chrome OS version 61, which is supposed to be pushed out sometime next month.
In addition to this change, the Peeking Launcher which is going to be a new launcher for all your installed apps on Chromebooks, is currently available to users on the Canary channel of Chrome OS and looks like what you might see in the stock Pixel launcher, complete with a search bar up top, listing your recently used apps first, and then expanding to show all installed apps if you scroll up. You can see what the Peeking Launcher looks like below in an image that was taken by Chrome Unboxed. Also live in the Canary channel right now is a back button that pops up in the taskbar. It's not clear if this is only going to show up for Chromebooks when they're put into tablet mode, but it's reported that this is when it did surface for its current state of development. Again, since these features are part of the Canary channel right now, which comes before the dev and beta channels, it might still be a little while before they make their way to the stable channel for all users.