I think swinging is about sexuality and monogamy is about relationship. The two aren't in the same catagory.
Yes, I think to return from swinging to monogamy is possible. Sex for sex's sake get's boring after a while. I do believe the choice can't be made unilaterally though, it would have to be a joint decision of both partners.
I live in the Netherlands and swinging is quite acceptable here. There are many private clubs and if you are so inclined you can pretty much always find something within a 30 mile radius.
Lately polyamory is getting to be more popular over here. Polyamory means to have the freedom to have more than one committed relationship. For me this is the only real choice. I'm not into casual sex nor would I go back to a monogamous lifestyle. I love more than one person and am proud of it.