According to Pacific Crest Securities analyst Evan Wilson, Nintendo has already finished work on the next iteration of the DS.

It is thinner (it has no GBA port), has on-board storage, and larger screens. However, we do not expect a revamped Wii or DS until sales begin to tail off in all three major geographies

No GBA port? On-board storage? Well, that fits in with Edge’s rumors about a new Game Boy download service for the DS, somewhat. Whatever the case may be, if Nintendo is really waiting for sales to drop before they release a new model, then it could be years before we see this redesign.

Analyst: DS redesign already done [GameSpot]

Read more: Nintendo Squashes DS Redesign Rumors, September NPD: Nintendo Leads Despite Xbox 360 Price Cut, DS Demo Downloads via Wii Coming Soon, June NPD: Wii And DS Lead, MGS4 Fuels PS3 Hardware Sales, Iwata: No Wii Or DS Price Cut This Year