I'm picturing a future where I go to the same park almost every day. (No specific park, but it's easy to get to from "the city," and big enough that you can find a section where the honking and smell of cars fades away a bit.) How does my understanding of the park change, when I come to know it like a friend? For example, I come to know particular robins who frequent the park (as well as particular human passerbys), I know which areas collect puddles in the rain, and which areas people are subconsciously drawn toward as the ideal spot for a snowman.
It's of the natural world, but it's also still of the human world -- after all, "the city" decided to protect this area, and the Friends Of clean up litter and host educational walks. You can hear the rustling leaves in the wind, the grasses under feet, the nesting of birds, and the occasional passing truck hitting a pothole.
So, it's not a "special" or fantastical future. It's special because it's familiar -- what would it be like to live in a place, and be of a place, where you can know a spot so intimately well? Rather than being transitory, chasing jobs or interests or affordable housing markets. (And of course, there are many other parks in "the city" which I have never seen; what drew me to this park?)
The garment for this future would need to be versatile! Four season. Resilient to mud and rain and snowball fights and getting snagged on a branch. Small enough and strong enough to be folded up into a backpack or bike bag. To me, an heirloom needs to be mendable, and also not *too* intricate that I'm afraid to use it. A few practical considerations: there might be ticks or poison ivy, and I don't want it to be too ostentatious (lest it attract chatty weirdos).
In this scenario, I picture a garment could serve as part of a daily ritual of the park. Put on the garment, go to the park. Or arrive at the park, and get the garment out of my bag. Its significance grows through habituation?