Sky need to do something - the value of them having a separate Kids pack (a decision which is relatively recent) is massively diminished without Disney. In terms of linear channels it’s now really just Nickelodeon and the two Warner channels. Mind you, it’s parents that pay and they may not follow all the channel comings and goings. The thing about Disney+ is that it’s not just Disney Channel content, it’s carefully structured to have something for both parents and kids (The Simpsons archive will be worth the price of admission for many older viewers alone).
Removing 3 channels with very low shares isn't that big a deal. The Kids Pass on NOW TV is only £1 cheaper, and I can't see Sky and Virgin Media reducing the Kids Pack by £1 especially when they already offer more extra 'channels'.
It would be a bigger deal if the Viacom or Turner kids channels were removed as they are more popular:
Disney Channel 0.7%
Disney Junior 0.9%
Disney XD 0.3%
Nick Jr 0.26%
Nick Jr Too 0.16%
Cartoon Network 0.21%
Those percentages suggest Disney have the higher shares, not lower.
Last time I checked the BARB stats, Disney XD had the same viewing share as or half of Boomerang+1.