Eldar isn't the first, nor do I think they'll be the last we'll see this from. Imperial Guard can bring a Baneblade, Orks have the Morka/Gorkanaut, Khorne Daemonkin have the Lord of Skulls, as well as the aforementioned Wraithknigt and Imperial Knights. We've already got Super Heavies in Codices. I fully expect Tau to get one of their Super Heavy flyers and I would expect Necrons to get their Super Heavies in their next Codex, even if that is likely a few years down the line.
Not to mention that rules are being printed in White Dwarf again, plus the numerous dataslates. It really isn't making me want to keep playing this game.