Print space in the main PHB is probably going to be a precious commodity, especially considering much much of the book Vancian Caster Spell List took up in previous editions now that they are making a comeback. Each race that gets in is going to need to carry its weight in terms of either Core Brand Identity common to the various world setting franchises (Core) or be a popular selling point (Modules).
The important part is to leave yourself easy design space for everything else!
Setting-specific stuff (Planescape, Ebberon, Dark-sun, Dragonlance) is more profitable (and orderly) to include in settings supplements.
Random leftovers (Goliaths, Shifters, Shadar-kai) can always be kept around to pad page-count for splat-books.
- Marty Lund
The important part is to leave yourself easy design space for everything else!
Setting-specific stuff (Planescape, Ebberon, Dark-sun, Dragonlance) is more profitable (and orderly) to include in settings supplements.
Random leftovers (Goliaths, Shifters, Shadar-kai) can always be kept around to pad page-count for splat-books.

- Marty Lund