I think that, by 2050, there will be a hit romantic comedy -- not a sci-fi story, but a modern-day tale -- about a married couple having an affair with each other.
At some point within my lifetime, we'll have the technology for people to quickly and painlessly change their faces and voices. (As distinct from the one-shot "Face/Off"-style identity shift.) It might be biological, nanotech, "magical," uploading your brain into different bodies, or people might have gone full-stop into robots by then; the specific method isn't important. The actual technology will probably be expensive, but that's never stopped movie protagonists before. (Filmmakers love to shoot flicks about high-powered glitzy professionals, anyway. Much better than telling the stories of the common rabble.)
Husband will be secretly leading a double life thanks to the technology above. He's got a big financial services job and stable but joyless marriage in Identity A (Al), and he's a debonair "old-money" playboy freely spending his "inheritance" and sleeping around in Identity B (Bob). Wife will also be secretly leading a double life thanks to the technology above. She's got a big job too, probably but not necessarily as a lawyer, in Identity C (Christine), and she lets her hair down in some unspecified but thematically appropriate way in Identity D (Debra).
Bob meets Debra. He pursues, she evades, then decides she likes the thrill of the hunt and draws him in. They have sex and both really enjoy it. Bob has had countless flings but never been interested in anyone before, and starts getting more and more obsessed with Debra. Meanwhile, Al has always been distant from Christine, but now that he's finding emotional connections as Bob, it's getting to the point she can't ignore. Christine, knowing that something is up but not of Bob's existence, decides she's going to tempt Al to test him. Debra puts her best moves on Al at lunch one day. Al refuses because he recognizes Debra. She leaves satisfied and he gets suspicious.
That night, Bob, intending to confront Debra, realizes he's left a MacGuffin at his (Al's) house; changes back and calls home. To his shock, Christine isn't there like she usually is. He forgets about Debra and drives home. Christine returns home after Debra can't find Bob, but her excuse for being gone is lame and Al starts suspecting something's up.
The next day, Bob shows up at Christine's office, posing as a flower delivery boy with a "Thanks for last night!" bouquet, intending to test her by gauging her reaction. Christine grills him, both knowing that nothing happened last night and recognizing Bob. He leaves satisfied and she gets a shock: clearly Al put Bob up to this and she needs to refocus.
So Christine resolves to stop being Debra for a while until Al calms down. Debra calls Bob, who was getting ready to deliver a wounded "aren't I enough?" lecture, and says they should cool it a while. Floored, he pleads with her to take a trip to Swanky Vacation Beach and reconsider. In a moment of weakness, she accepts.
Christine then has to justify going to Swanky Vacation Beach, so she buys Al a trip there on the same flight as an anniversary present. In the meantime, Al has already had the same idea to cover up Bob's trip, and all three sets of tickets are scheduled for the six first-class seats on the same flight. Bob and Christine both delay their SVB trip due to Important Business Meetings, saying they'll be on the next available flight; and so Al and Debra are left totally alone in first-class. Awkwardness ensues. In an attempt to keep her from hitting on him, Al tells Debra how much he loves his wife. Debra, flattered, apologizes, spills her own dilemma, and asks what she should do about Bob, who she really has fallen for. Al, flattered, tells her she should go for it.
They check into adjacent swanky hotel suites at SVB, and Bob and Christine dash back to the airport to "arrive" on their "later flight". Bob grabs the wrong wallet from his luggage: the one with Al's ID and cards.
Bob drops his MacGuffin Wallet in the airport restroom. Meanwhile, Christine quick-changes and Debra calls Bob to tell him she'll see him back at the hotel. When she gets a voicemail from Al saying he can't pick her up at the airport, Christine forgets to turn Debra's cell phone back off. They both head to the curb to hail a taxi. Christine recognizes Bob and approaches him to pry more details out about the flower thing, and Bob fidgets and tries to find an excuse to leave -- until he realizes his cash is all gone. Christine pounces: she'll cover the taxi ride if he spills the beans, and they can both hook up with their significant others after reaching the hotel. They both get into the taxi.
The Bob/Christine conversation goes pretty smoothly. Bob heads off her questions by gushing about everything he loves about Debra. It makes Christine nostalgic and she starts listing off her husband's best qualities. Then a good Samaritan finds Al's wallet and calls his wife's phone (Al's is off). During the phone call, she realizes it was lost in the exact same place Bob lost his, and finally puts two and two together. Meanwhile, Bob pulls out his phone to send a quick text message update to Debra. She hangs up. He hits "Send."
"Oh my god, Al?" *beep* "Oh my god, Debra?" Cue horrendous argument over infidelity that slides inexorably into the realization that it's each other they were really looking for all along. Implied makeup sex. Sappy ending on shores of SVB.
Yes, I know, it's so heteronormative it makes your teeth hurt. It could be a much more compelling story if it played with gender identity or gender roles or relationship structures (imagine how much zanier the comedy would be if you had a poly triad Alex, Jamie and Pat). But, even in 2050, there are going to be limits to what Hollywood will allow in a blockbuster.
Absolutely none of the above happens in the latest Legend of Hero, although there is some mutual unrequited desire goin' on. Peter and Hope take a walking tour of the Shadowlands in Wandering Merchant Joix: Act I, and end up at a location that should be familiar to regular readers ... the plot threads, they begin to weave together.