In June 2014, Apple announced the discontinuation of development of Aperture. Since that time, Apple has released five major macOS updates. For technical reasons, Aperture will not run in future versions of macOS after macOS Mojave. To continue working with your Aperture photo libraries, you must migrate them to the Photos app included with macOS, or migrate them to Adobe Lightroom Classic.
Apple has provided instructions on how to move your Aperture libraries to Photos or Adobe Lightroom Classic in this support document.
In March, Apple also warned users that as part of the upcoming transition from 32-bit to 64-bit, legacy media files in Final Cut and Motion won't be compatible with future versions of macOS. You must convert your legacy media files before upgrading to macOS 10.15 because the option to convert the incompatible files will no longer be available after macOS Mojave.
The next version of macOS will likely debut at Apple's Worldwide Developers Conference in June. Please follow iClarified on Twitter, Facebook, Google+, or RSS for updates.