All three companies (Nintendo, Sony and Microsoft) have signficant risks built into their hardware strategy, but I'm not sure that this is really the main risk for Sony ...
In my opinion, Sony's greatest weakness is that they produce very unimaginative hardware that could be described as being enhanced versions of something that has come before. This makes it (fairly) easy to anticipate what Sony is going to release, and allows their competition to anticipate weaknesses in their strategy long before they announce their systems. It could be argued that Nintendo's more "unpredictable" strategy with the Nitendo DS, Wii and 3DS are in direct response to this; and Nintendo has countered more powerful hardware by producing more unique and interesting hardware.
