Canelo Alvarez is gonna make a FORTUNE for his fight against Gennady Golovkin ... with Oscar De La Hoya suggesting he could break $50 mil when the dust settles. 

Oscar joined the guys on the "TMZ Sports" TV show on Wednesday when we asked straight up if Canelo would clear $50 mil. 

"It's gonna be a no-brainer," Oscar said ... "He's gonna make a lot of money, let me tell you."

And while Oscar wouldn't get specific with exact amounts, he did reiterate -- "The purses are gonna be huge."