December is a bad month to release a system in any territory because then both the launch hype and holiday hype cancel each other out. I'm going to predict November or earlier for Europe, if they can get shipments done quickly and efficiently, there could be a huge number of systems sold at the launch, and also another huge number sold to holiday shoppers the next month, then it's up to momentum.
June for Japan is too early... unless it's out in other territories at that time as well, I think a worldwide launch is the most important thing to focus on. Plus Japan still has the DS causing riots in the meantime so there's no rush.