the point being the ps3 is only slightly cheaper than Xbox360 and Wii put together is the worse thing that can happen to the ps3....
buying an xbox360 will let you play many types of games SIMILAR to ps3...so not too many people will get both...on the other hand the Wii is a very good second console consider the rumored $299 launch price....intuitively the best combination would be buying xbox360 and Wii then skip the ps3 altogether....this way you get both "traditional" games on xbox360 AND new experience with the Wii...
to be honest I start to think about getting xbox360 now and get the Wii on launch date.....and completely forgo the ps3 until at least 2 price drop......