Oat milk[1] is the next fad after soy, almond and coconut milk. These are mainly for people who are lactose intolerant, although perhaps some people who aren't lactose intolerant prefer a different taste for lattes or cappuccino drinks.
In the US I believe there’s now also another type of milk called A2 that doesn’t have certain forms of beta-casein proteins[2], which allegedly will help ease the discomfort lactose intolerant people feel after they ingest cow's milk.
[1] https://www.nytimes.com/2018/01/19/style/oat-milk-coffee-oat...