Given the length of announcing the original DS and then releasing it (urgh, I still have Nintendo's first announcement email, back when the DS was ultra fugly)... I'd say it will be announced next year, shipping 18-24 months later.
There's a lot of bite left in the DS and a massive market. Plus several core Nintendo IP's still haven't made it to that system (so the GBA gets how many F-Zeros?). No need to kill a perfectly healthy cash cow.
And I'd like a touchscreen like the iPod Touches/iPhones. Be it single or multitouch - that surface alone is brilliant. And they best be b/c with DS games and hopefully still sport a GBA Slot 2 option (for expandability).