“Future disciples” means that Buddhism is a teaching which has a limitless future and beginningless beginning, which should always be true. So, in the sutra there are many disciples and buddhas who will exist in the future and who existed eons before.
—cuke.com/ig for links to the source of the photo. Excerpt from Shunryu Suzuki lecture 68-10-00-C as found on shunryusuzuki.com, edited by PF. Go to instagram.com/cuke_archives for the Instagram version.