[roc]

That seems to be a de-facto-standard away from being solved though. Someone, or some collection of someones, are going to hit on a controller and/or case and/or variant device that establishes some set of inputs that clicks with the market. [1]

And developers will design for said standard and that will be that.

That seems much easier (if not entirely inevitable) than Nintendo discovering some way to halt and/or reverse the trend away from dedicated gaming devices.

[1] a standard along the lines of the modern console: "dual analog sticks, d-pad, shoulder buttons, four face buttons"; or stand-up arcade fighter's: "analog stick + 6 buttons", etc. It doesn't have to be one-true-piece of hardware, just a general arrangement of inputs that developers can design for.

[jessedhillon]

I don't think lack of hardware or standards here is the issue. It's still an open question as to whether those same people who buy mobile games would walk around with a controller+phone in their pocket/purse.

[roc]

The question isn't whether happy touch-gamers would buy these controller cases in bulk. The question is: should these cases exist and get developer support, how many 3DS and Vita gamers would continue paying a premium for their dedicated devices and software libraries?

Android and iOS already "have" the larger slice of the market. (The "touch gaming" slice) My point is that they're a very short step away from essentially taking "all" of it. (Not literally all -- focused devices may still live on -- but enough that Sony and Nintendo's current model can't sustain itself.)

Also, I think you're "off" on the size estimate.

Extend a hypothetical mobi-style battery case an inch-and-a-half on the 'head' and 'chin' of an iPhone. D-pad on the left, some buttons on the right -- maybe even shoulder buttons if you're feeling saucy.

The result is still pocketable and smaller than a Vita or 3DS. (Similarly for any number of popular Android phones -- though phones with 5" screens would push the arrangement directly into Vita-ish dimensions.)

Stand-alone controllers are an important part, but they'd be something that provides consistency on the TV-screen side, with things like GameStick, Ouya and/or Apple's rumored AppleTV gamepad play.

[Karunamon]

Designed correctly, it would be no larger than the portable game console.

Something that looks like this, for instance: http://www.cellphones.ca/images/news/2008/11/iphone_keyboard...