I'm going to guess Nintendo gives me a birthday present and releases the NX info on Sept 30.
No other reason, just specifically for Neogaf Forums Junior Member Hilarion's birthday.
In all seriousness, people here take the Eurogamer leak seriously, as I do, and then completely ignore the "Unveiling in September" component and wonder what's wrong that, in the definitely-not-September months of July and August, nothing has been announced. If you buy Eurogamer that the NX is using Tegra, if you buy from Eurogamer that the system is a hybrid with detachable controllers, why is the "info briefing in September" part hard to accept?
What sort of sane company would unveil a major product during the middle of the Olympics, anyway? Of course Nintendo isn't going to put the NX info out right now.