Eh, I'm not so convinced. Capital didn't allow slaves to be replaced with paid laborers out of the goodness of their hearts, but because slavery became obsolete - it's simply less profitable.

If you've got a bunch of enslaved workers, not only do you have to keep them alive (i.e. provide some minimal amount of food/shelter/medicine), but you also have to keep them in line and prevent them from just running away. That means you need to employ guards (enough to stay above some minimal ratio of slaves to guards), which is an additional cost. Not to mention that people generally don't enjoy carrying out forced labor, so your slaves will likely not be as productive as possible.

Now, if you take the same group of slaves but convince them that they're "free" and are performing voluntary labor in exchange for some form of monetary compensation, the whole equation changes. You can just pay each "wage slave" the same amount that you would have been paying yourself for necessities, plus maybe a token amount on top so that they can occasionally access a little bit of luxury and keep morale up. You don't have to pay to maintain a guard force (now the guards can also be employed as ordinary laborers, increasing your labor pool!), and workers will probably be more productive on average since they get to feel like they're getting something in return for their effort. It's literally just more cost-effective than slavery - the former slaveholder has fewer costs, lower risk of their workers revolting, and better performance per-worker.

The calculus got a bit imbalanced for the better part of the last century, since the rapid and continuous economic growth throughout much of the world (the Western imperial core in particular) meant that there was enough surplus that workers could actually sustain a decent level of luxury expenditure on an ordinary salary. Now that growth is slowing down Capital is just clawing back the territory it allowed to get taken during the glut. I don't see us returning to actual slavery, but something more like how things already are for much of the working class across the imperial periphery and developing nations (or like things used to be in the imperial core; think British factory workers in the mid-late 19th century): shitty working and living conditions, and long working hours in exchange for barely enough pay to scrape by.