You should download the Workflow app right now and test it out to see what you can do prior to the private API hooks that will come in Shortcuts. As it stands, I've got a workflow on my phone right now that lets me convert a 4K video to 1080p, adjust the speed on the video (helpful if you shot in slow mo and want to export a smaller full-speed video for sharing). Don't even have to launch another app. Just trigger the workflow from the Share Sheet.
There are workflows for automatically stripping the status bar out of screenshots, creating an on-the-fly playlist for songs you haven't played in a certain period of time, or even deleting all your completed reminders from the Reminders app. Don't get me wrong, it's not for everyone, but being able to trigger it via Siri will make it a lot more popular.