That would have been too much change to the way things work ATM. Maybe this will happen at some time, but i would have to redesign quite a lot of stuff for this, so don't hold your breath...you might run out of air...
Edit: Maybe i should explain this in a little more detail: Adding shader support would require to have some kind of hardware only pipeline. jPCT doesn't have this ATM, because the OpenGL render pipeline still uses parts of the software renderer's pipeline. That's why i call it hybrid. I'm still having plans to add a real HW pipeline on an object base (by "locking" the object), but i really don't have the time nor the need to do that ATM.