The DS is really due for an upgrade. After all, while it used to leave the PSP in the dust (in terms of sales), it's now neck-and-neck with the PSP sometimes outselling the DS. Problem especially in Japan, is not that DS is waning, but probably because everyone who wants one already have one, and that includes the extended DS demographics (Brain-age crowd, female crowds, etc.).
A midlife upgrade seems plausible, as the GBA had numerous times. the PSP is upgradiong too soon (PSP 3000) and that should spur sales, so Nintendo must have something working, my guess is that it will be minor instead of big upgrade. With a new and big upgrade coming in 2009.
TGS is coming soon, so any news should come there. If not, then it's just rumor. Unless, it's already in production, Nintendo would be stupid to preannounce it and miss the Christmas selling season.
Location info like GPS? Nobody have been able to make any good GPS game, so unless Nintendo new device have a big screen, it's no-use as a map reader, GPS. And wouldn't be able to beat the iPhone especially if it can't integrate with Google maps.