What might be interesting is the NBA could be at the top of the tv bubble right now. League revenue isn't guaranteed to increase forever. If the value of tv deals go down even a little, that could lead to some interesting situations in 2025 when the next tv deal goes into effect. That's still a couple of generations of players away though, but down the road in 2022, 2023, 2024 we might see some interesting salary dumps if the cap is projected to go down.
Looking at the tv deal:
They signed their current tv deal with ESPN and TNT in 2014, and some people think they overbid as they had exclusive bidding rights and didn't want others like Fox or NBC to get the chance to bid. Also they were pretty much the only sports deal available until 2020 with the Olympics (expires 2020), MLB (expires 2021), NHL (expires 2021), NFL (expires 2022), World Cup (originally expiring 2022, now 2026), March Madness (expires 2024), as well as all the football conferences other than the Big 10 already locked into deals.
Most of those tv deals were signed between 2010-2012, and it's been reported that cable tv subscriptions peaked in 2012 and have been declining ever since (at increasing rates too I believe).
Then we have this current news with ESPN laying off 300 employees, and most of those reports focus on cable subscription rates declining, which was a big source of the revenue that companies used to bid on these deals. ESPN charges cable companies like $6+ right now to carry its channel, and it's built into their contracts to actually increase. I've read reports that said it's set to go up to about $8.50 in 2018.
So cable subscription rates are declining (with many people blaming the high costs) while the cost to carry sports is increasing. So to offset the lost subscriptions, they raise the price, which causes more people to cancel? Welcome to the death spiral.
Sure cable companies like ESPN can go à la carte and offer streaming subscription services, but with pirating and sharing accounts that will come along with the high price I'm sure they'll charge, I don't know if that will be the savior the industry is hoping for. Especially when people pay $10 for Netflix, $10 for Hulu, $20 for ESPN, $15 for HBO, etc. As much as the consumer says they want to go à la carte, they also don't want to subscribe to several different services to get what they want.
While I don't see sports ever going away, I don't think it will always be the same revenue driver either. There's a ton of industries (music, radio, video sales and rentals, print media, etc.) where many probably thought the good times will last forever that are now on life support. Sure they still exist, but they aren't really making money anymore. Think of when things like when the tech bubble or Real Estate bubbles burst, a large part of that was because the prices kept getting bid up as the investors thought the values would continually increase. Then you suddenly realize people aren't buying at the price you thought you could sell at. This is where I think sports is headed, and if so the salary cap is going to have to take a hit at some point which will lead to the price to take a salary dump to go up.