While it is pretty early to worry about the Core Rule II+ books, my suggestion is to apply a similar ruling as we recently passed for LEW/LEB - Only the original SRD (which is supposed to be released pretty close to launch) content, namely PHB I, DMG I, and MM I, are available by default. SRD content from books thereafter (which seems likely given the quotes on Psionics being in a PHB and Psionics entering the SRD) needs to be approved separately (hopefully the SRD content won't be intermeshed to be inseperable). I would go a step further and recommend that races playable out of the MM need to be approved separately. While gnomes will presumably be playable out of the MM, there may also be others, such as warforged.
The Core Rule II+ books are also part of why I think that an exploration aspect is so important. Even if not all new stuff gets approved, some will, and it helps if we have undeveloped areas where we can say, "Yes, psionics is pretty strong there", for example.
Bookkeeping:
We are pretty certain that the 4E class list at launch is : Fighter, Paladin (Defender), Cleric, Warlord (Leader), Wizard, Warlock (Controller), Rogue, and Ranger (Striker). We know there are eight classes, and only the paladin and warlord aren't exactly confirmed yet.
We are pretty certain that the 4E race list at launch is: Dwarf, Eladrin, Elf, Halfling, Half-Elf, Half-Orc, Human, Tiefling. There may be more races, and one or two others might not make cut. There are more playable races in the MM.
We know the broad strokes of the default cosmology, but we don't know yet how much of it will end up SRD content.
Tieflings and warlocks work together to paint a less-than-bright image of the 4E world, but we don't know yet what form alignment takes (if any).