I tend to agree with you, to a degree. Nintendo has positioned DS in such a way that it doesn't compete head to head with either the PSP or iPhone/iTouch. Sure, iPods are everywhere, and Apple has stated that iTouches are selling well, but I have yet to see any hard numbers on the iTouch. Whatever it is, the DS has a huge lead in installed base, and even the PSP most probably has a good lead. So, given that the target decmographic for DS and iPhone/iTouch are quite different, I don't see any danger to the DS. In certain areas there is overlap, and there Apple has a chance, but overall I don't think the iPhone/iTouch sales will have any impact on the DS sales.
Now, regarding your other point about non-gamers, that's a valid argument and I suspect Apple will gain traction there, bringing people who normally game very little into handheld gaming. However, I don't think those people will change their iPhone/iTouch for a DS/PSP because of the convenience factor, and the price of games. Remember that you can buy games for a fraction of the cost on the iPhone/iTouch, and whenever you want just as long as you have a network connection. Why would a person who is used to games costing a few dollars, max 10, switch to another device and pay manyfold for the games that often have to be purchased from a retailer?
