I'm going to make a prediction: Nintendo will launch around September. I think/hope the company is aiming to launch as early as possible, but it will probably delay in order to improve the games. I'll even put it in my signature.
Nintendo can deal with the issues of a worldwide launch by not trying to release it right before Christmas. I think that's what's hurting MS: Christmas was always Microsoft's deadline, and missing that deadline is a big deal. If Nintendo is shooting for June, it can delay a month or so to pump out some extra systems. There will also probably be less of a buying frenzy than with Christmas launches. I don't think there was ever a big supply problem for the PSP or GBA, on the other hand, DS, PS2, Xbox and GameCube all had varying degrees of supply problems.
I'd like to see Revolution launch as early as possible (bearing in mind that a good launch lineup is a must). If Nintendo is serious about earning more market share, it should try to launch less than a year after the competition! Of course the counter argument is that Nintendo is aiming to capture new markets, but those new markets may not be receptive. I like Nintendo's plan to attack new markets, I think the company sees that the gaming market is still immature...it's something they potentially understand better than anyone else, even if Nintendo's home console sales aren't the best. I think Nintendo is smart to try and expand the market and make it more approachable but I think it would be bad to make a move on new markets without any concern for the existing one.
About E3: I don't think we need to worry about Nintendo unveiling everything at E3 and launching one month later. If you look at what Nintendo has done the past few years, it has been pushing games prior to E3 more. Unless Nintendo isn't planning to launch until the end of 2006, I think we'll see some Revolution games before E3 - maybe at GDC.