Never. Slavery and white mastery is vindicated. Brazilian and Cuban elites feel emboldened to defend their social order forcefully. The political reality of having intervened on behalf of, and having close relations with a slave state leads British conservatism to de-emphasize abolitionism. It becomes associated with religious fanatics, socialists, and other reformists and discontents.
By the turn of the century, the long running American trend of land and slaves ending up in fewer hands in the south leads to a system of massive plantations with thousands of slaves. The price of cotton has declined from its heyday, but new markets continue to open and the Confederacy is king in quantity and quality.
Poor whites have been emigrating to the US by the millions in search of land and factory jobs. Confederate industry remains overwhelmingly light, labor intensive, and under-capitalized, relying on slave labor, much of which is slack labor from the countryside, which has its own light industrial base on the plantations. All attempts to adapt modern steel production processes and manufacture of engines and factory machinery to slave labor have so far not produced profitable enterprises. As a result, most Confederate military production potential is by state owned armories using skilled white laborers, which is fine as few southerners would be comfortable with slaves assembling guns and shells.