You don't know casual boxing fans? A casual boxing fan is someone who doesn't follow boxing on a regular basis but when there's a big fight they'll watch. That line about being a fan or not isn't true. You can be a casual fan of something. I wouldn't call myself a fan of soccer but I follow it because I need to for work so even though I won't watch MLS matches most of the time, i'll watch Premier League when it's on.
And you need to make sure you read things before you comment on them. I specifically said boxing will never die because of hardcore fans and the popularity of the sport internationally. But boxing in the United States is behind the NFL, NBA, MLB, UFC, NHL, Nascar and Soccer in terms of relevance.
Mayweather is the last name remaining that casual fans are interested in paying to see. Boxing has done a TERRIBLE job over the years building up new names. Go ask a someone who says they watch boxing every now & then who Canelo Alvarez is and most wouldn't know. My brother i'd consider a casual boxing fan and when I was over his house to watch the Mayweather fight he asked me who would he fight next and I rattled off 3 different names and he knew none of them other than Amir Khan. Will boxing go on after Mayweather? Of course. But tell me who is drawing in the casual fan?
The Mayweather-Guerrero fight was advertised during March Madness, they had a 24/7 type show on Showtime, they had advertisements in magazines, but it still couldn't do 1 million PPV buys.