E3 was THE time to show your stuff, even if it was just words. The system isn't ready yet, but you had their attention. Some of those who don't currently own a Nintendo console probably checked in to see what Nintendo's up to every year at E3, and they probably did it again with Zelda.
No info until the fall? If not, is it going to be a separate Nintendo event that isn't Tokyo Game Show? If so, you've already lost the attention of millions who had their eyes and ears open at E3.
For Microsoft, they've done it. We know what's coming. We know more about it than the NX. We know that it's going to be powerful, and could be something to delay purchasing plans of those who were probably interested to see that the NX is going to be about. ...and to see that no one's really saying much about supporting it, including Ubisoft, who chose only to say that Just Dance will be there, doesn't help.