A Japanese Nintendo Direct is set for May 31st at 6 AM EST (3 AM PST), a couple weeks before E3.

It's specifically designated to cover games coming out in the summer (in Japan). So don't expect the unexpected.

Link.

Overall, I'm pretty excited for Nintendo's showing once we get to E3. A lot of people are being negative around the net, saying the Wii U is a failure and they've already announced a bunch of games, so there's no need to announce more. I don't really get that mentality. The Wii U's output has been great lately (don't care if it's a financial failure) and the last 2 Nintendo E3 digital events have had the most surprises out of the bunch.

They must be pretty confident in their E3 line-up if they can afford one more show 2 weeks before.