It seems that Roto Grip has decided to "simplify" things and put 3 balls in each category. One solid, one hybrid, and one pearl. The only exception is HP4, where they currently have a solid, a pearl, and the urethane. I suspect we will get a hybrid later on. And that's maybe when they drop the wreck em for a new pearl.
The only issue I see, is that they may be going solid, hybrid, pearl, but I'm not sure they all follow as strong, medium, weak, like they are implying. And that's the problem with marketing. I still think they need to drop the HP naming scheme, or at least change it from "hook potential". It doesn't match up.