With the Wii version of Pokemon getting a serious amount of attention about online play, the lack of DS information is puzzling. Many think that Pearl/Diamond will be completely without online compatibility. However, Nintendo quashed that rumor, saying the online play is there; they prefer the fan base to create their own buzz.
Being mum on the next big Pokemon's key feature isn't quite surprising. Nintendo has never had a problem moving handheld Pokemon titles. Nintendo is most likely choosing to focus their efforts on promoting the console version of the franchise, which will have an additional benefit of moving more Wii consoles in the process. Don't worry, Pokemon fans, you'll be throwing down with people around the nation in Pearl/Diamond.