This should give us some ideas to think about. Trending niches can be lucrative. The trick is to come up with a monetization strategy and then get there first.
What do you think? What niches might get popular in 2020? Well, it will be 100 years since the 1920s which brings up Roaring Twenties, art deco, shorter dresses, swing dancing, and Jazz music.
Amazon products back in vogue?
20s style clothing
Art Deco memorabilia
What about fan pages in these niches?
Ebooks and short stories?
Prohibition / Mafia / Gangsters