The Apple conference on the 12th will be devastating for both handhelds and consoles. Iphone 5 and mini Ipad will compete to get consumers money from handhelds and consoles. Money is little and the hip devices right now are smart phones and tablets. The Galaxy 3 did 20000000 in a 100 days which is amazing.
Okay...people need to start taking the hard logic they put on dedicated handhelds and put them on other systems too.
Iphone 5 will just compete with other smart phones and upgrades from 4-5 - it won't have any increased effect on the handheld games market than general smart phone growth. Its unimportant, iphone is already affecting things.
mini Ipad will maybe have some effect...but also on apple goods. People will decide which Apple good they want. Iphone owners will not get it but go for an Ipad (too similar) whilst Ipad owners won't both either. New customers coming in will look at the different devices and weight up their option.
The ipad mini will mostly sell to people who own another smart phone than iphone and want that same interface/experience/brand in some form or another.
In the end its more competition within the tablet market, I don't see how it suddenly changes the handheld market. In the end ipod touch has been out for years.
Its not going to increase any effect on the 3DS and thinking it will is misunderstanding the market. If iPad mini is a success, it'll affect the sales of other Apple devices but likely will bring in some new customers but those are customers who'd chose other devices anyway.
Its not a big shift in the market in any sense; but very internal.
EDITED to add: It may actually see some upgraders from ipad to mini, wishing for a smaller size. I was in Berlin last week, tourists taking photos with an ipad is the most idiotic thing I think I've ever seen. I think they believe the entire back side is a camera - rude too as they block the view