Your neighborhood - post Homo sapiens

So what will survive if we all move out?

At my old house, within 5 years, it would be an oak forest with a frothing of Virginia creeper.

It is not even predominantly oak right now. There are two pin oaks and a burr oak within the block. And lots of other trees. But it’s the oak sprouts that everyone fights all year long.

Mine would be a forest of elm and green ash in no time flat - the boulevard trees seed all over the place. My neighbours already have the beginnings of a forest because they haven't kept on top of the seedlings.

This is unless emerald ash borer and dutch elm disease attack. In that case we'd probably end up with poplar everywhere. This biome is called "aspen parkland" for a reason :) There's a fair amount of spruce, some pine, etc. Also there are lots of species like lilac, caragana, cotoneaster, and mountain ash that have escaped cultivation and are thriving, and a few hardy oaks.

My new place in town in Kentucky would soon be elm with redbud along the edges. I still haven’t identified which species/variety of elm; but those are what I find most frequently in the garden and lawn. My neighbor across the street has the great granddaddy elm in her back yard. It is an awesome specimen. My next door neighbor has a young volunteer elm right on our property line. She climbed it earlier this year to cut some of the branches scraping my siding and roof.

My house on the Carolina coast will conceivably be underwater by the time the young live oak in my front yard reaches maturity.

I have a few acres out of town in Kentucky too. I used to think it was the blackberries that would take over the world. But after two years of very little mowing, it’s the locust and sumac trees that are the pioneers, followed closely by tulip poplar. With cat briar winding it’s way through everything.
I’m taking down 25 foot locusts in the side yard. And, of course with the piles of brush, I still can’t mow.

Edmonton has a huge river valley running through the city, which has been lived on for thousands of years by the indigenous peoples, and for the last 150-200 by settlers from "away". It's mostly parkland now (aside from a few old neighbourhoods on the river flats) but there were Chinese market gardeners in several places in the early to mid 1900s, and although their gardens are sadly long gone, you can still find their legacy of feral horseradish, rhubarb, asparagus, goji berries, and other things, if you know where to look :)

Silver maple trees. They come up everywhere from my neighbors trees that were planted 40 years ago. Also, poison ivy and wild violets will take over.

Where I live, on the KS/MO border, my neighborhood is full of mature oaks. But I think the land would become more like the acreage I own a bit north of here, on a hill above the Missouri River: a jungle of wild roses, grapevines, and a variety of trees, including oaks, walnut, maybe osage orange (though it might have a problem with propagation), and a scattering of less-common trees like paw paw. All of these grow, or have grown, on my land, as well as others.

My entire state, Michigan, would quickly be overtaken by giant oak, red oak, and evergreen trees followed by the return of statewide marsh lands. The state originally was one big marsh with mastodons roaming to the salted grounds in the middle region. Canoes were the only way to get around on and between the Great Lakes back then. The land would soon become very wet again with an explosion of green.

The front garden runs out onto the edges of a partially drained bog. The peat here has probably shrunk away six feet or more. The first thing to happen will be the drainage breaking down, re-wetting the surviving peat and recreating the sphagnum bog. It's all only a few feet above sea level, so probably destined to be vast salt-water mudflats before the end of the century. Good for samphire for a while?

The back garden is part of a strip of oak woodland on one of the few "islands", patches of dry land in the bog. It was probably coppiced until the Great War, but is now pretty well packed with bluebells and wild garlic. Post Homo sapiens (and more to the point, post Ovis aries!), this is probably what will invade local fields and gardens, plus the trees in the hedges: hazel, hawthorn, blackthorn, lime (EU 'linden', US 'basswood'?), elm (which I noticed in hedges everywhere during local lockdown walks, despite having been eliminated as a tree by the 1960s-1970s Dutch Elm Disease) and ash (which is having a pretty torrid time of it with Ash Die-back).

Oh yes, and the pernicious aliens: Rhododendron ponticum, Himalayan balsam, Japanese knotweed and Buddleja davidii.

If I moved out, the wisteria, honeysuckle, and PRIVET would take over quickly. Oh, and Virginia Creeper (which doesn't creep as much as race across the yard!)

I've placed old carpet on the front yard slope (no HOA) to smother the honeysuckle and poison ivy (yep, that too) that have grown over my spreading junipers.