I think we need to approach this topic from two perspectives: Functionality and aesthetics. Our bodies are the interface between our minds and our environment. The functionality of a body depends on its requirements. How do I want to interact with the environment around me? Since most of the environments we live in were shaped for humans, having a human-like body should be a sensible choice in most respects.
Functionality
Different environments
We could decide in the future to adapt our bodies to the environment, rather than the other way around – or more realistically settle for something in between. Living on a space ship poses quite different requirements than living on a planet. Dealing with microgravity would probably lead to bodies that look at least somewhat different from regular human bodies. The ability to do spacewalks without a suit would also be a neat plus. Robotic bodies with integrated propulsion and cooling systems would be quite suitable for that.
If people want to live under water, they should eventually look more like dolphins, sharks, or squids.
Living in large vertical cities might be more convenient, if people had strong, powerful wings.
Durability, resilience, and longevity
Having a body that can repair itself effectively would be a huge advantage. Our current bodies can recover from wounds, but can’t regenerate whole limbs. We can deal with most germs, but some of them may kill or cripple us. Upgrading our bodies, so that they can deal with all these problems would be a big advantage. Also, bodies that don’t age would obviously solve a lot of problems. Having bodies that embed titanium or carbon nanotubes into the bones on their own would be quite advantageous.
Sensory faculties
Bodies with better senses would be interesting. The ability to perceive electric or magnetic fields, or electromagnetic waves of various frequencies naturally, would be quite useful in many situations. Seeing light in different frequency ranges would also be quite nice – especially in the heat vision range of infrared. Being able to smell concentrations of various gasses exactly would also be advantageous. Are those car exhausts really dangerous for you? Currently not sure, but if you can smell their composition, you would probably get a more intuitive understanding of that (though we will hopefully mostly use electric vehicles, before we develop the technology to improve our sense of smell like that).
Optimized forms of metabolism
It would be quite useful to recharge your body energy via an electrical outlet. Electric energy is cheap compared to food. Some bacteria do have the ability to sustain themselves on electricity alone!
Alternatively, being able to digest cellulose efficiently would also be quite useful.
Improving cellular metabolic pathways would be quite awesome, because doing more with less energy is always a good idea, wherever possible.
Aesthetics
Aesthetics are subjective and inter-subjective. While people have their own preferences, the cultures surrounding them, will have their own norms and preferences. Satisfying either one will become increasingly simple, as our ability to create and modify customized bodies improves. But satisfying both at the same time, will remain a challenge. What if I want to look like a quadcopter drone, but my neighbors complain about the noise? What if society expects from me to have a body with four arms (because that makes me a more productive member of society), but I find them aesthetically displeasing? We won’t solve such problems with technology alone.
Each culture will need to develop its own rules and norms to deal with the possibility that some people have prosthetic limbs that can be effectively used as weapons, or want to become slithering blobs that secrete sticky slime wherever they go.
Having a population with high morphological diversity may come with lots of challenges. But the other extreme would also be problematic. A population consisting of people looking like 20 year old white men dressed in uniform business suits would reduce frictions, but may suffocate creativity and freedom of expression.
Self-expression
The body you present to the world also may express something about yourself. In a future in which not only humans are citizens, but also artificial intelligences, uplifted animals, and possibly extraterrestrial species, would look quite different than the one we currently live in. These groups will probably have quite distinct aesthetic preferences. Robotic bodies would probably be more popular among AIs, and uplifted animals may want to switch to therianthrope bodies:
https://transforum.fractalfuture.net/t/towards-therianthrope-morphs/2243
Mixed bodies would be the next step. Human, animal, machine, alien, and custom parts will be used more and more by the different parts of the population. There will probably be many trends based on incorporating or mixing such parts. Eventually, wholly new customized body morphologies will be created. Dragons and other fantastic beasts may roam the colonized worlds. And our imagination in the future will give birth to even more fantastic body forms that people can choose from.