Afaik true rebalancing isn't in the works. Some limited add-device and remove-vdev features are in progress but AIUI they come with additional overhead and aren

Afaik true rebalancing isn't in the works. Some limited add-device and remove-vdev features are in progress but AIUI they come with additional overhead and aren't as flexible. btrfs and bcachefs rebalance leave your pool as if you had created it from scratch with the existing data and the new layout.