Charles has spoken of downsizing the number of working royals for a long, long time ... it is one reason why Eugenie and Beatrice went out and got jobs after college, as they knew they would not be working royals.
No, Charles has NOT spoken about downsizing. Sources close to him, even Prince Philip in the late '90s/early '00s, recognized that the general public opinion was not in favor of having a bunch of "minor" royals performing royal duties rather than working in the private sector. To that end, it was made clear to both Andrew & Edward that their children would not have public roles as working royals. To their credit, both Bea and Eugenie understood the message, earned their college degrees from good universities and went to work in the private sector. They both seem happy and content with their lives, and they're both happy to, like their "non-royal" cousins, Zara & Peter, step in and help out with things like garden parties or occasional appearances on behalf of the Royal Family when necessary - like this spring with Kate's cancer diagnosis. Same goes for Louise and James, though they're both still in school. My guess is that the six cousins will likely "tag in" and help out from time to time as events that align with their personal interests occur, to help bring a little youth and glamour to the Royal Family until the Wales children are old enough to take on more public responsibilities.
The plain and simple fact is that the intention was for Harry & his wife, as son and daughter-in-law of the direct heir when Charles was still POW, to fill the role, in a much fuller way, that is now getting filled in by the other cousins. The people who have benefitted most from the Sussexes bowing out aren't Charles, Camilla, Kate & William - it's Edward & Sophie, who have definitely increased their profile in the past few years; Anne, whose presence and support is demonstrably valued and appreciated by Charles; and the Duke & Duchess of Gloucester, who are as active and supportive of the Crown as they have ever been - and Charles recognized and honored Brigitte's tireless service this year by making her a Lady of the Garter.
The Sussexes could have had all that, in due course, but they weren't satisfied with having to follow orders (of the Foreign Office who schedules all the "royal tours" to other countries; of the sovereign who has far more life experience and one might argue a better finger on the pulse of the nation than, no offense to Meghan, a new immigrant and her spouse who apparently had a lot of unaddressed mental health issues that made him arrogant and difficult to work with behind the scenes), nor were they satisfied with not having the spotlight on themselves at all times - and, really, failing to understand that, due to the very nature of what a monarchy is and how inheritance works, they were never going to be the top dog all the time in the chain and their role was always destined to that of ensemble cast member who sometimes gets a featured solo but often times does not.