Currently there is a trade in various hippopotamus body parts, but if the animal was listed as endangered, this would cease to be legal.
Currently there are between 115,000-130,000 (though other knowledgeable experts can put the estimate as low as 80,000) but it is not what is happening now, so much as the threat that hippos are believed to face over combined threats of climate change, poaching and habitat loss.
Certainly, of the large species of Africa: Elephant, Rhino and Hippo, only the Hippo is regularly found outside protected areas (the Congo basin rainforest is perhaps different, but this may not last).
Given the threats currently, along with changes that are likely in the next few decades, I believe it is certainly time to include Hippo as endangered , on CITES level 1. Hippos are currently listed under CITES level 2 which allows some trade.
From 2009-2018 77,579 hippo body parts were traded around the world, so it is clear that we should act now. Were the hippo to recover across its African range, this might be a decision that could be reviewed, but for now it seems prudent to stop the Hippo slide towards extinction.