Office.js preview features release

Office.js for PowerPoint has had a couple of preview features (getImageAsBase64, getSlideAsBase64) in preview now for nearly a year. 

I've done my best to search for any updates from the office.js on release timeline for these features with no luck. 

These two API calls are super convenient and enable features in the add-ins for PowerPoint which is near impossible to create using alternative solutions. 

Anyone out there with any knowledge on when we can expect these beta/preview features to be production ready?