I read and heard about how nowadays its very rare to find wild ayahuasca. What one finds is either cultivated or the spreading of old cultivated species. Many indigenous people also cultivate ayahuasca, and so did their ancestors.
Ayahuasca that is sold is all cultivated AFAIK and I havent ever read any credible sources to say cultivated varieties is in any danger. Daime people for example have huge ayahuasca plantations that supply the use for thousands of followers. They are required by law in Brazil to be sustainable in their harvest.
So one way or another, ayahuasca is gonna be there, its easy to grow in tropical areas by directly sticking a small section of the vine in soil. Indoors in higher lattitudes maybe people could grow too, but I dont know how effective that would be for harvesting.
I dont know though about the exact source of the vine gotten by most ethnobotanical suppliers, and neither have any idea of the real numbers of how much aya is bought in this kind of market.
Whatever way it is, though, I think that if one can grow caapi, its highly recommended. Growing plants is great, gives you a whole new connection with life