Late 2016: Newly published Chrome apps will not be available to Windows, Mac, and Linux users (when developers submit apps to the Chrome Web Store, they will only show up for Chrome OS). Existing Chrome apps will remain available as they are today and developers can continue to update them.
Second half of 2017: The Chrome Web Store will no longer show Chrome apps on Windows, Mac, and Linux.
Early 2018: Chrome apps will not load on Windows, Mac, and Linux. There appears to be two main reasons why Google is killing Chrome apps off now. First, as Google explains in a blog post: "For a while there were certain experiences the web couldn't provide, such as working offline, sending notifications, and connecting to hardware. We launched Chrome apps three years ago to bridge this gap. Since then, we've worked with the web standards community to enable an increasing number of these use cases on the web. Developers can use powerful new APIs such as service worker and web push to build robust Progressive Web Apps that work across multiple browsers." Secondly, Chrome apps aren't very popular: "Today, approximately 1 percent of users on Windows, Mac and Linux actively use Chrome packaged apps, and most hosted apps are already implemented as regular web apps. Chrome on Windows, Mac, and Linux will therefore be removing support for packaged and hosted apps over the next two years."