I am not sure if this counts as a threesome... well, maybe a selfish one. I fantasize about a 2 + 1 situation (the + 1 being my husband, watching me with another woman). But a true threesome, with everyone fucking everyone regardless of gender... naah, I don't know if I'm up for that.
I'd still be willing to try the 2 + 1 in reality, if we get to that point (and can find a suitable participant, for both our tastes). Still enjoying just the two of us, at the moment.