It seems that Square-Enix still can't get enough of the DS, and following the success of Final Fantasy III, (especially in Japan) the company is looking at continuing its good fortune with a remake of Final Fantasy IV for the DS. The game will utilise the same graphical engine and style of FFIII, and first scans show that they have even improved it slightly. Final Fantasy IV (alought unreleased in Australia) was recently only remade for the GBA. Update: Scans inside.
Source: NeoGAF via Famitsu Magazine