Nintendo is traditionally very very conservative for their estimates. So don't look for them to give out an estimate that exceeds analyst opinions. They seem to give a conservative estimate, and then beat it each quarter. So the "pop" is more of a gradual quarter by quarter thing.
Currently the DS makes up as much of Nintendo's sales as the wii. I think one concern is that the platform is gaining market saturatioin, and the PSP has made very good inroads into the market. So the DS may not have as much growth left as the Wii does.
The other is that many Wii buyers find themselves content to simply play wii sports.
I really don't think the PS3 or XBox really affect NTDOY that much. At the end of the day the core market is the same,.