I will argue tennis is dying at least in the US.
1.) Major fan base in the US and player base in the US I believe is 60+ Younger base is not replacing them. These guys are going to start dying. Most clubs have a bimodal member base--under 18 and over 40.
a.) General sports fans have little idea who anyone is outside of the Big 3, the Williams and a handful of other players.
b.) Most tennis fans know only the big stars and their own personal favorites.
2.) Pickleball is pushing tennis out with all the money and current popularity of pickeball in the US.
a.) ESPN is choosing to show PB over tennis.
b.) Tennis Channel is choosing to show PB over tennis
c.) Tennis courts and clubs are either replacing tennis courts with PB or making them into PB/Tennis courts. A lot of aging fans are jumping to PB.
d.) General sports stores are replacing walls of tennis gear with PB gear
e.) My girlfriend left me for a guy who just learned PB tonight.
3.) USTA juniors are struggling to fill tournaments. Kids often drop out of competitive tennis due to time demand and high coaching demands or rampant cheating and poor organization of USTA.
4.) US has a plethora of public tennis courts--where in many areas are rarely used, growing over or PB
5.) Coverage of tennis shifting from major networks to ESPN to Tennis Channel and even on tennis channel you have to either join 3 other networks to see everything, taking it out of the mainstream and making it a niche sport.
6.) US used to have more 500 and 250 tournaments, now they are leaving.
7.) Many pro tournaments are empty mid week. Making tennis look pathetic. Try to hype up a match of #30 vs. #25 and then you see no one there.
Yes, I see how masters are still busy and slams are selling out. I think there are a few factors there. First, devoted tennis fans know what tournaments to go for for the best bang for your buck. 2nd, I think a lot of corporate seating buy seats but leave them empty. I think in the past tennis was big enough, that general sports fans would watch tennis. Now only tennis fans. so those of us that remain go to the slams and masters. Sure we'll go to a local 250 or 500 if we live nearby, but we aren't going to fly or take off work to see a 250 unless a star is there.
8.) It's hard to make a living in tennis unless you are a top 200 player, and even that can be tough.
It might have a resurgence, or this also might be the future of sports in general as people are less active and media has more and more to compete with.
Maybe in 10 years, there won't even be a tennis channel you just pay direct to watch the match you want and choose what commentator you want.
The sky isn't falling, but the ceiling is much lower.
Tennis has always relied on stars. I always wonder if there is some way to promote/market the sport as a whole. Or make people aware of the top 100.