It would be interesting to inquire as to how far their [Turbine's] Liscence of D&D material extends, and if it is in any way limited by the OGL which is attached on almost all D&D 3.5 source material.
Bottom line though, even if they are not playable, Kalashtar at least deserve their own model in game.
Its not like we're asking for Tauric Bears or anything like that. (I keep meaning to look up exactly how the Scorrow happened, its an interesting Drider variant, but I don't know how the Drow did it without the aide of Lloth.)