The concept of playing DS/3DS games on WiiU is far from old - there are references to the idea back before the WiiU even launched (As well as an instance where Iwata was asked about it). His response mentioned "Consumer need," which has me believing that Nintendo is going to continue their intelligent business tradition of giving their fans what they want if they actually take the time to ask.
Everything that's needed is already available in the console, sans any necessary processing chipsets and - of course - a 3DS slot. This means that manufacturing could be done relatively cheap (In comparison to the Super GameBoy, which was a GameBoy that powered itself VIA the SNES Console and fed it's video to the SNES frame buffer)
Alternatively, they can offer DS/3DS games to the virtual console. This would be cheaper for Nintendo to pursue, but more expensive for the consumer.