It won't be a new raid or they'd say so. There might not be another raid until they launch the big expansion next September. What I'm thinking is they'll keep adding new encounters to The Leviathan. It's a huge ship. And all we did was explore the castle on the top. Calus told us to seek him out at the end. So it would make sense to have more encounters. That said, I'd prefer it to be more like the others, and less like this one. I don't think it's bad, like a lot of people do. But I prefer more boss fights, than challenge rooms.