I don't think that swinger life is going down. I think swinger life is just fine :)
There is a ratio though. I am not sure of the accuracy of this ratio, it's more of a tongue in cheek guess.
100 Single males to 10 couples to 1 single females.
We do not actively look for single females, single males or even couples. If someone/some couple catches our fancy, we will put forth effort.
What we have noticed and this is purely anecdotal and applicable to us. When we moved from South Florida we left behind the club scene. We could go to an on-premise club and we would do this 3-6 times a month. We would have no problem finding either another couple, a single male and most of the time, if there was a single female that piqued our interest, her. Now that we are sans club life, it's all about hotel/house parties. What is odd compared to most others is that I, the male, am the very picky one. My wife is not a slut per se and that she will fuck anyone. She has a lot more acceptance of men as partners than I do of women. This does make things a little harder when we are looking for couples.
I bring this up because, well, we have been in the lifestyle since the early-mid 90s. We have seen pretty much all the scenes you could imagine. What we have learned though is that it is really about effort. If you put forth the effort, you tend to get results. If you sit and wait, like the girl waiting for the prom date to call, you will not be as successful. I think once you have been in the lifestyle for a bit, you tend to get complacent and just 'expect things to happen.' You tend to forget that when you started you were out there, putting forth effort. Saying hi to people. Hoping you would not be rejected. We had to realize that when we hit a dry spell that it was not the lifestyle that had changed. It was us. Once we realized our change, we remedied it and voila! It was back to the way it was earlier.