What you should do is encourage anyone to learn Buddha Dhamma.
- Whether anyone can even be a Sotapanna depends on that person’s abilities.
- Each person will make progress in their own way. Of course, one may become a Buddha if one cultivates all the requirements; that usually takes a long time, certainly not within this life or even within this eon (Maha Kappa) because the next Buddha to appear (Buddha Maitreya) is already in the Tusita Deva realm.
- But there could be a few Bodhisattas in the process of fulfilling those capabilities.
This idea that anyone can be a Buddha, like Buddha Gotama, is a Mahayana idea. See “Key Problems with Mahāyāna Teachings.”