How did it ruin the season? This was likely to be the outcome even without Durant.
I think it might ruin the next few seasons when it all becomes repeated over and over, but this season has been fun. The utter dominance of the Warriors has been breathtaking.
Owners wont see profits taking any major hits the next years. Most teams are locked into TV deals already. If anything they will get more money because a handful of teams are starting to pay insane amounts of LT. The NBA was at it's peak viewership when MJ was dominating the league. Casual fans enjoy dominance, not parity. It only really becomes an issue if there isnt some kind of noteworthy antagonist to challenge them. Lebron is always going to be there though (at least for the next handful of years), and that will be enough to drive ratings.