ZFS is still great and for many things the only choice still.
But it will quite certainly never be a native (in-kernel and distribution default) filesystem for linux, due to licensing and patenting.
Btrfs didn't reach feature-parity yet, but the developers promise that it will. And it will be native and not patent-encumbered. We need a filesystem like that on Linux, because ext4 doesn't have all the advanced features (especially checksums in the metadata). Therefore it's very good for the health of the linux ecosystem that it exists.
"The storage used for the MDT and OST backing filesystems is partitioned, optionally organized with logical volume management (LVM) and/or RAID, and normally formatted as ext4 file systems. The Lustre OSS and MDS servers read, write, and modify data in the format imposed by these file systems." (from wikipedia)
It does feature a ZFS storage backend though.