The Tokyo Game Show is coming at the end of the month. I don't know if Nintendo is going there (they usually preferred Shoshinkai/Space World, but they cancelled those), but Sony is going to TGS, and taking the PSP with them.
That close to the apparent launch, Nintendo has to have a better show than Sony (and they'll have some sort of showing, whether inside TGS or not, just because they have to). If the PSP has a more exciting show (or if the DS is a no-show), the DS will be in serious trouble. If the DS beats the PSP, the opposite will be true.
Nintendo can get themselves ready for the launch behind-the-scenes without needing to tell us squat. The current problem (that we know of) is that they're not getting the public ready for the launch. But TGS and strategic competition with the PSP seem like they'd be the major factor in that.
I just hope that Nintendo has more than "more refined versions" of the E3 games, and more hands-on time with the DS (along with explanations of things, of course). They need some surprises and secrets to reveal, or they might be in trouble. A lot of people thought the PSP beat the DS at E3, even though the PSP wasn't even playable, just because "it looked more sexy". Playable PSP games with superior graphics are probably enough to win over a lot of people. Unless Sony kills the PSP at TGS, by telling people what they didn't want to hear about the price, or something like that.