In Nintendo's recent quarterly investor Q&A, president Satoru Iwata discussed the possibility of an HD-followup to the Wii. "If asked if making the Wii compatible with high definition -- just making it compatible with high resolution -- will get players throughout the world to buy it," he said (as translated by Andriasang), "I would of course say, 'Do you think it would sell with just that? It needs something new.'" Note that his statement isn't a denial of an HD Nintendo system at all.
Iwata also addressed the contested statements he allegedly gave to the Asahi Shimbun about a DS successor. The newspaper reported that he said it would have motion-sensing and "highly detailed" graphics, a claim that Iwata later said was "misinterpreted." Iwata helped clarify the situation further in the investor Q&A, suggesting that the reporter led him to that statement.
According to Iwata, the reporter asked, "The next DS will need to have high resolution graphics and include a motion sensor, wouldn't you say?" to which he responded, "Those are naturally considered requirements. However, do you believe it will sell with just this?" All together now: It needs something new!