I've seen a tiny handful of developers juggle more than one file system at a time. They're that complicated. I'm familiar with most of the Btrfs developers and

I've seen a tiny handful of developers juggle more than one file system at a time. They're that complicated. I'm familiar with most of the Btrfs developers and can't think of a single one who works on ZFS; the most active developers when asked about it quite a few years ago on the Btrfs development list said they were unfamiliar with ZFS and it wasn't used as a guide for Btrfs. You can track developers through their git commits, and you'll see even when they change companies, they almost invariably keep working on the same filesystem they were before the move. Which is why the idea that Red Hat has no one working on Btrfs, means they want to see it go away is not what's going on at all. They have a lot of other developers already, who'd lose years becoming familiar with Btrfs (or ZFS for that matter). So you're going to see them build on what they already are familiar with, rather than moving laterally to a filesystem technology they're not familiar with.