And Reggie himself confirmed it during Nintendo's E3 2012 presentation. If support for two GamePads was never meant to be, Nintendo shouldn't have announced support for two GamePads. If people complain it's okay to address the complaints, but it's not okay to give empty promises to your customers.
Support for two GamePads is highly unlikely to come to the Wii U at this point, so let's just focus on there being only one. As I laid it out, the Wii U can technically run at least a 1080p screen (TV) and 720p second screen (Wii U GamePad), but it remains to be seen whether that happens at 60fps or 30fps. I believe the reason there would be a performance hit is because there's not enough bandwidth in the wireless transmission to support more than two FWVGA screens at 30fps each. E.g. if we take mirrored content and want to send it over to two GamePads, this would be done by sending every other frame in a 60fps stream to each GamePad. But because we don't have to support two GamePads, it's possible to have one GamePad running at twice the resolution (2xFWVGA = 1138x720) at 60fps. This is only theory that without any more available information is hard to prove, but if we work with the information that's available to us now, this is a plausible theory.
I'd love to hear your comments. If I left something out, feel free to criticize.