Yes, all images that have been resized and replaced in your store will remain even if you cancel your plan. 

If you’re on a Free or Pay-as-you-go plan, we will store the original images of the product images we have resized for 7 days, from the moment the images have been resized.

After 7 days, you will no longer have the option to restore the images back to their original files, unless you upgrade to one of the paid plans prior to image expiration.