Call me a pessimist, but I think neither will do as well as its predecessor. 3DS has the 3D going for it but I don't think it will capture the DS audience that Nintendogs and Brain Age built. Also, price.
The NGP, well, there are still many unknowns (like the price), but I find it hard to imagine it will fare much better than the PSP did. I think that at best, it may capture a large audience in Japan late in its life, once the Japanese developers start firing on all cylinders for the thing. But in the West, I think it will suffer from the fact that a lot of the PSP purchases were done with the intent of hacking the thing. If the NDG is less hackable, I'm sure hardware sales won't be as high. Plus, those people arlready have a piece of hacked hardware they can play SNES roms on, they don't need another.
I also think the increased competition from phones will hinder both systems.
It sort of seems like Nintendo intentionally made the 3DS more of a hardcore gamer's machine this time around.
Maybe...and why not? With such a mass audience entertained with the DS (including DS lite/i/xl) it's almost the perfect time to introduce something with a little more..kick. This could be a strategy used for the Wii's successor: Bring in a new expanded audience with something 'new' then bank off of it with something more advanced yet similar to the newly established gamer..
The DS has been around for awhile..I don't think the 3DS will outsell it for a few years but it has the potential to..I think any new Nintendo handheld does.
Assuming this strategy actually works for Nintendo, where do you see the new audience that the DS had failed to reach come from?
I just can't see the 3DS doing better than the DS. I see a bunch of people not upgrading their DSes because it meets their needs just fine. Many will upgrade, but a lot won't.
I don't think 3D has the pull that the idea of "training your brain" or "raising a virtual pet, talking to it" has on the vast majority of people out there (casuals, you might say, the audience Nintendo needs to reach again). And I'm not sure it will draw tech fetishists, I think those people are too busy waiting for the moment they can get in line for the next iteration of the iPad, or looking forward to the NGP.
So yeah, I see people leaving, and I don't see people coming in to replace them. Much like the audience shrank going from the NES to the SNES, despite the SNES being obviously better. The previous machine was good enough for them, and they got over it and didn't need more.
I think the 3DS will do better than the DS. The DS had a slow start with games for the first year or some, the DS3 seems to have a muhc better start. People seem to love everything in 3D too. Even crap movies like Avatar.