However, according to a report obtained by GamesIndustry, the processing power could have been further reduced. The original build for Natal included a chip that processed the "bone system," assumed responsible for creating a skeleton of the player in front of the device's glossy eye. However, in an attempt to lower costs, the chip was removed from the device's final build, putting that processing onus on the software that will utilize Natal.
In other words, it's extremely unlikely that any software will be able to have Natal support patched into it -- a fact that Digital Foundry's Richard Leadbetter says could help "serve to focus developers on Natal-specific concepts as opposed to revisiting old classics."
Update: Updated language to reflect that of the original source -- Natal will use 10 - 15 percent of the 360's overall computing power, not just its CPU.