I spoke with Tom with Jende Industries concerning this issue, and he had this to say:

"If anything, I see the JP stones eventually replacing the Pro stones, not the glass, but there are no signs of Shapton making other JP stones right now.

IMO, the glass stones are too aggressive for Japanese plane blades, which seems to be the JP stone's intended market. Overall, the glass stones (white) are better suited for straight razors."

So, it appears to me that the JP stones are between the Pro and Glass but only come in 4k & 8K options. So, considering that there isn't a complete "system" of them, and we know that Shaptons don't play as well with other systems as other hones, it would seem pretty clear what the course of action is.

Just my $.02