Many moons ago it was mentioned in passing on the Tome Show by a designer that the Psionic Leader would be the Empath.I had that same thought initially, but then it occurred to me... We don't know what the other psionic classes are going to look like. If (just for instance) the psionic leader turns out to be more in line with the kalashtar, that'd be just fine. I think they need to be "aimed" at a psionic class of some sort, but it doesn't necessarily need to be the psion itself.
I'm willing to bet that the Psionic Leader will be using Cha or Wisdom, considering it's based on Empathy.