not every Wii games uses motion control, or even the Wiimote

What is more alarming is how developers are going to utilize 3d when it is optional(slider controls "how much" 3d you have). Either not all games are going to require 3d, or none of them will if we go off of that. I think the first option make more sense. 

I think most games wont require it, but most will look better if 3D is used, probably only a few will actually require it

The only problem I see is there won't be as much action going on on the bottom screen, if any at all. All of the game's action will occur in the top screen, while the bottom screen will be mainly utilzed as another form of control for the player, a touh panel.

There's a video (I don't remember where) of Nintendogs and Cats where the player can interact with the dog using the touch panel.  The dog is displayed on the top screen, but there is a silhouette of the dog on the bottom screen. so interacting with the silhouette dog directly affects the dog on the top screen. I don't see any issues with this, and I imagine other games will work in a similar fashion. I can see something like a pointer apperaing on the top screen when using the touch panel. 

There really isn't any need for both screens to have action, especially considering the top screen will have 3D.  Don't expect any action to hop onto the bottom screen.

I don't know how this has to do with anything. I'm asking how developers will develop their 3DS games when they can't simultaneously do 3D and on screen touch/pointer manipulation on the same screen, limiting or vastly changing how certain games we're accustomed to on the DS will now perform. Let's look at one particular game, Trauma Center. This game is controlled by directly manipulating items and doing actions on the touchscreen that are being shown on the touchscreen, not the screen above. The only thing on the screen above is your timer and a static image of your assistant giving text based instruction. How does a developer keep the same fantastic touch based gameplay while simultaneously providing a 3D experience for the user if each is presented on a separate screen?

Change the setup, make the lower screen something like an outline of the patient, and the upper screen the image, so you make the cuts and such on the lower screen, but the upper screen shows the effect of the cut in 3D, it'll force some creativity out of some developers, not a bad thing imo

interesting arguments, you might think that the '3D' games only use the top screen and the bottom screen is only for DS backwards compatibility and control layout

not necessarily, imagine Advance wars 3DS, the battlefield can still be depicted on the lower touchscreen, but the animated battles, can be shown on the 3D screen for example, anything that won't be dependent or greatly improved by the 3D effect can still be displayed on the touchscreen.

Seems a bit pointless, but mainly because I've played and understand the mentality behind developing Trauma Center. It's a game about precision, working against the timer, and quick actions, so continuously having to work between both screens would only slow the game down, since you need to look at the bottom before touching the touch screen which means you're not looking/enjoying the top screen action and you can't merely slide the stylus around and pay attention to the top screen since that would greatly limit the actions you could perform. 

This is really what I was getting at is what experiences we expect from the DS would we lose with 3DS development. It won't merely just be a slight tweak and everything is honky dory with every beloved DS series. Some will have to be radically changed or merely go away in exchange for new experiences the 3DS will excel at. The point of the thread is to discuss what can be salvaged (and how) and what can't. Frankly, if the big fix for every game is going to be some outline on the bottom screen to accommodate for the action taking place on the top screen, I'm going to see that as a major disappointment, as it takes away your attention from the action in quite a few mentioned series, just like quick time events tend to do for many people on consoles, and even leaving gaming, what native language subtitles during a foreign move do for many also.

The problem is that you are still forgetting, that 3D is not required, the game could just say, please turn off the 3D effect before playing, and viola, keep the old style if it works better, same way some games never use Motion controls on the Wii