Should CABAL_DIR really be dropped in the future?

There was a [recent question](https://stackoverflow.com/questions/68079550/clean-installation-of-haskell-onto-a-windows-10-machine) in Stack Overflow, dealing with how to put the files related to Cabal in a non-standard folder. That question has a pretty straightforward solution which consists in setting the [`CABAL_DIR`](https://cabal.readthedocs.io/en/3.4/installing-packages.html?highlight=CABAL_DIR#environment-variables) environment variable. Once set, the configuration, the store and other cabal content will be contained in the folder `CABAL_DIR` points to.

However the user guide [says the following](https://cabal.readthedocs.io/en/3.4/installing-packages.html?highlight=CABAL_DIR#environment-variables):

> The CABAL_DIR might be dropped in the future, when cabal-install starts to use XDG Directory specification.

Following the XDG specification is a good idea, but should it require abandoning `CABAL_DIR`? That would forgo some versatility.

A good compromise could be following `CABAL_DIR` if defined, and follow the XDG specification otherwise. Alternatively, perhaps the burden of maintaining both options is not worth it?