Details have surfaced of a patent registered by Sony for a "removable adaptor" that can be connected to a "next generation games machine" with the codenames for both devices, "200" and "300", possibly hinting at an external PS2 backwards compatible adaptor for the PS3.Translations of the Japanese text in the original patent describe how the adaptor would work and explain that the "200" adaptor would be like a revised version of prior hardware and a hub would act as the connector for both devices and an optional router.
Although reports are keen to highlight that this is only a patent application at this stage it would be interesting to see if Sony makes this more concrete and would answer many PS3 fans prayers by charging them for the means to play PS2 games as well, albeit in an external hard drive attachment fashion.
Source:
Siliconera