Investors won't care about E3 much. They'll be more interested in areas of immediate business growth, particularly how amiibo is doing and when we can expect the first smartphone games to launch.
There'll be some questions about NX, too, and about when we'll see that and what kind of hardware it is.
EDIT: Also, some stuff on the new loyalty scheme/network improvements, and the usual semi-vague slides about future plans, including Quality of Life. I'd also expect sales figures for amiibo, Splatoon and other key titles to feature in Iwata's presentation. Perhaps some slightly more concrete statements on where Nintendo are targeting their development resources, perhaps even an admission that with Wii U selling so poorly more resources are being put behind NX to avoid a repeat scenario.
