Father Tony, it'd be great to have you write in more depth about why you hope the 'straight vs. gay' dichotomy has gone stale. What kind of potentialities do you imagine? Grounding 'fluidity' in some practical, lived way is always of interest.
Fluid sex. Schedule it for 2020.
Glad you asked because I have been having visions of the way it will be.
In the old days (pre-pill) sex was strongly fused with reproduction. It was an unhappy marriage assured by the fact that all successful species evolve with a built-in friction-as-pleasure feature and an innate pheromone response that make the males and females of the species mate despite the fact that they don't really get along. (Many rabidly heterosexual males actually hate women. Ask any woman, if you doubt me.)
Uncoupling sex from reproduction was a big step toward understanding and appreciating the attractions that happen in our heads. Uncoupling birth from the womb (100% lab babies) will be the next big step. Cloning, in which I provide a few skin cells to create a replicant or three for organ harvesting, as ego-gratifying descendants or just for narcissex will be a final giant step in human sexual maturity that will help us sprint ahead of other primates.
Along the way, techies and geeks who get laid infrequently and who also understand the huge market for safe sex will perfect virtual sex to the point where we won't have to wear clumsy goggles or attach diodes to our privates. Users worldwide will say "Damn that was better and easier than the real thing!"
Men will stop marrying women when they realize that they don't have to put up with the work that is entailed in a heterosexual marriage just to get laid well and often. Hanging with their buds will cross the final frontier of male bonding. Women will live with women and have affectionate sex with women when they are finally rid of any need for men in the baby-making business. Marriage will be based on love and devotion rather than fecund friction.
Ah! Are you following me on this? Do you now want to accuse me of thinking that all men and women are basically homosexual at heart and that the only reason they consort with the opposite sex is for the survival of the species? You should, because I'm not so sure that is not the case.
Eventually, after several generations of purely homosexual activity, our species will mature to the point where folks will have sex with men or women without regard to their equipment and with attraction based solely on the health and personality of the individual. It will be an era of renewed sexual exploration. When that day comes, we will have finally become adults. Eventually, the evolution of our species will erase the physical male/female differences and the unused internal reproductive organs will disappear. The pleasure generating buttons may disappear along with them, or, they may become larger because we like them so much. If they disappear, our species will be freed from the nuisance of sex altogether, and our replication will be an entirely intellectual decision made with altruism and with a sense of duty to the universe. (Incidentally, the same thing may happen with our ingestion of food which is tied to pleasure so that we will do it often and remain strong and healthy. If we devise a more efficient nutrient delivery system, our stomachs and intestines will become vestigial and eventually disappear, followed soon by the demise of yet another nuisance appetite. All that will be left to us is a thirst for wisdom. And all of you biologists out there needn't bother jumping in to inform me that I have a simplistic notion of evolution. I already know that, thank you, and I intend to keep it that way. It's pretty.)
I think I have arrived at this thinking by having a lot of sex and analyzing it ad infinitum (and ad nauseam to some). I see in our current culture, a dismantling of taboo and fetishism that will change the way many people have sex in the near future. We are each currently victimized by parenting that demanded of us in our formative years some level of repression and denial and prohibition. As we permit everything and show everything and have access to everything, we will fetishize nothing. We will be sexually obsessed with nothing. We will turn to personality as an attractant and we will couple with men or women whose personality appeals to us.
Odd, isn't it, that most religious groups think that the fruit of promiscuity and sexual liberation is the surrender of a man to physical desire for body parts. The opposite is true. Once you've sampled all the body parts available on men and women, the only elusive goal is the individual human personality which becomes the ultimate aphrodisiac.
I figure we are about 11 years away from the stage in which we have sex with anyone regardless of their sexual assignment, age or ethnic/racial markings. Our sexual attractions will become based on the health and personality of the sex object. I'm already there, and I'm now waiting patiently for Colin Farrell and Halle Berry who will still be hot in 2020 to finally walk hand-in-hand into my boudoir where the door is always open.