Two months ago, Nintendo announced that they were partnering with Japanese publisher DeNA to release mobile games. To assure fans that Nintendo was still focused on dedicated gaming platforms, Iwata also teased new hardware codenamed NX. No real details were given for NX, and it looks like that's going to be the case for a while. After stating that Nintendo won't discuss smartphone games at E3, Iwata reiterated that we'll have to wait until next year for NX news, but he did leave investors with the teaser that NX is not a "simple replacement" for Nintendo's current consoles.
"We do not plan on talking specifics about the the NX until 2016. Presently, we cannot talk about the time period when it [the NX] will go on sale or what it’s like. Because we are calling it a ‘new concept,’ we are not thinking of this as a ‘simple replacement’ for the 3DS or the Wii U.
"Incidentally, we’re getting various questions for this year’s E3, like ‘Won’t there be a NX announcement?’, ‘Will there be a presentation on smart devices?’, or ‘Will there be more on the quality of life platform?’ However, since we understand that E3 is an event for dedicated video game machines, we do not intend to discuss the smart devices as well as quality of life." — Satoru Iwata
NX being a "new concept" is the only detail that Iwata will say. However, the fact that he sees it as something other than a replacement to 3DS and Wii U is very similar to how Nintendo originally treated DS. Prior to its launch, Nintendo stated that DS was meant as a separate device to be sold alongside Game Boy Advance rather than a replacement for it.