The Xperia play probably failed due to relatively weak games available compared to a 3DS. So you have a phone pretending to be a games console, you might do better by adding phone functionality to an already strong gaming system.

Now I'm seeing the potential for the successor to the 3DS to be the (I assume) first 3D videophone device.

I think this is unlikely, but I'm charmed by the idea.

Fair enough. Seems easy to put an on/off switch on the side, though, like laptops have for wireless. Then you can just turn the phone off during your tough gaming moments.

don't forget the nokia n-gage

Actually... I mean the n-gage. The Neo-Geo was an older system. Just a similar name >_< (both have "n" and a hyphen in it...)