DEPR: pd.Categorical

[jbrockmendel]

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Reproducible Example

NA

Issue Description

Categorical predates general EAs, and is the only EA directly in the pandas namespace. Could we deprecate Categorical as being public and tell users to user Series[cat] or CategoricalIndex instead?

Having it be public makes it modestly harder to make improvements. e.g. #40996 would be easier to implement if it weren't user facing.

union_categoricals is public and operates on Categoricals, which would be weird if Categorical were made private. Maybe something like #51362 making pd.concat behave like union_categoricals would make union_categoricals unnecessary?

On the flip side, Categorical is special, and some of the special-casing of it internally isn't likely to go away. So maybe we just live with it?

Expected Behavior

NA

Installed Versions

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