The below statements are all conjecture.
Duergar* - Psionic race for Psionic Power Source. Their "demonic" nature (as described in an earlier & article I believe) will be tones down to Tiefling levels.
Githzerai - Psionic race for Psionic Power Source. Also popular with the Planescape "implied setting" in Manual of the Planes I and II.
Gnome - A popular race left out of PHB I. The MM entry is not a full write-up, and they're generic enough not to go into a campaign guide.
Half-Orc - A popular race left out of PHB I. Also likely Primal to support the Primal Power Source in PHB II.
Shifter - A popular race in 3.5. Also, the Shifter Ranger in Races & Classes suggests they are considered for Core play. Also likely Primal to support the Primal Power Source in PHB II.