Microsoft has an app available on the Windows Phone Store that helps you prepare for new updates. UpdateAdvisor makes it possible to conveniently remove temporary and unnecessary files to free up some space. Should you find yourself to be tight on free room on your smartphone, and have uninstalled all the games you don't play, this may be the perfect solution for you.
The app not only connects to the internet and checks for new updates, but also provides suggestions on which files could be moved to SD storage and OneDrive to help make room for required system files. Give the app a download and see how much space it can free up before making the jump to a new release.