I really don't know. The GB line lasted 12 years ending with the GBA. The DS line has lasted 5 (going into its 6th year) We probably won't see a new one until 2011-2012. Hell, if sales continue, we may not even see it for half a decade....

Nintendo had a handheld console ready a couple of years ago but decided not to release it. This was probably a next generation Gameboy. At the time, Nintendo probably were still not entirely convinced the DS could continue their handheld dominance and were probably worried about the PSP, but Nintendogs, Brain Training, New Super Mario Bros. and Mario Kart DS put those fears to rest and another console was no longer needed.

With that in mind, the thought of Nintendo having a DS 2 and Wii 2 sitting there isn't hard to fathom but they are not the final boxes. Nintendo are continually making changes and adjustments as can be seen with the evolution of the Wii remote from TGS 05 to E3 06.

So in my opinion, we can't know what the next DS or Wii will incorporate as Nintendo doesn't even know. If it comes out next year then it may be similar in design to the DSi but if Nintendo waits even longer we could get something like this:

I think we will see the next handheld platform revealed at E3 2010 for release Christmas 2010. Its been five years now and Nintendo rarely breaks that cycle. Remember the GBA had the SP and Micro before the console was replaced. Now the DS has DS:Lite and DSi and now the new larger screen, if Nintendo sticks to their past marketing strategy then we will see the new handheld launch next Christmas.

Now the DS is still selling extremely well. Some would argue Nintendo might ride the DS's success a little longer. If they do choose to stick with the DS then I expect a new handheld to be unvieled alongside WiiHD at E3 2011! Can you imagine if WiiHD and the next handheld launched the same holiday season?

Of course I don't think Nintendo will launch the next handheld the same year as WiiHD. The handheld would take sales from the home platform and vice versa! So my best bet is Christmas 2010.

Actually I can see Nintendo being very, very, very interested in a folding LCD design.

That's pretty damn neat if I say so myself. Would it be doable in a product in the sub $200 price point is another question altogether though.

Nintendo is a very intelligent company...One thing that I'm sure everyone's noticed that they've done differently with the Wii and DS though is that they've expanded their audience to include EVERYONE. I see soccer moms playing crossworDS and brain age on their DSs en route via public transportation.

I can see the DS 2 with hints of Wii in it (ie like the iTouch/iPhone motion control apps) and much improved graphics with *hopefully* backwards compatibility. But anyways, back on topic, the DS 2 probably won't be on store shelves anytime soon. Hell, God forbid it, but with all this talk about Apple and those stupid iPhones, we might even be nearing the end of the handhelds as we know it within the next 5-6 years.

They've already snuck in a hardware upgrade. Isn't anyone aware that the DSi cpu is clocked 2x that of the original DS and has more RAM and a better screen?

There just isn't a portable gaming system out there that can threaten the position of the DS enough to force Nintendo to launch a successor. I can't even conceive a portable system that can. I'm sure Nintendo has the 2 screen system patented well that competitors won't find loopholes. Whomever, will come up with the next step in portable gaming, and I'm not talking about better graphics, if it's not Nintendo would definitely force Nintendo's hand.

Apple is a bit of a concern. Pretty sure even every kid will own either an iPod touch (as more and more that becomes the standard iPod) or an iPhone.

They're everywhere. As for the overclocked DSi specs ... is Nintendo even planning on doing anything with it? It's been about a year since the system launched in Japan and still not even a peep on that really from any major developer. 

This doesn't make any sense to me. It's debatable whether Nintendo makes the best games (in the eyes of gamers). Some people here even prefer Sony as a first party.

What is not debatable, is that their ability to create appealing software for the masses is unrivaled. Nobody even comes close. Sony or Microsoft are incapable of pulling off something like Brain Age, Nintendogs, Wii Sports or Wii fit. This is the reason why they're so successful this gen, not because Super Mario Galaxy has a 97 on metacritic. There's obviously something in those games that people like more than their competitors (or lack of).

As for the successor to the DS (or Wii, even), I have no idea what they'll do. The DSi already has a touch screen, mic, and a camera, what more can they add to draw users in? I do think it's possible the successor will be mainly an upgrade in power, to keep people busy until they can find "the next big thing."

Hard to say when Sony or MS really haven't tried. I guess maybe there's EyePet on the PS3 and that "Lets Go To The Movies" game on the 360 but really  don't think either has put a huge effort into courting the casual market -- yet. 

In the past Sony has had some success with things like Eyetoy on the PS2, PaRappa on the PSOne, and so on. I wouldn't say Sony sold 100 million+ PS1s and PS2s just off of hardcore players. Things like Crash Bandicoot and Spyro also helped them back in the day. 

Nintendo will release a new handheld and console, when one of two things happen, one, their system is no longer selling the most on a yearly basis or their competitors next gen hardware becomes a threat, as neither has happened, or looks to happen any time soon, it'll be a few more years, 2-4 at least before anything new is released