To be clear, here’s how ZD Net summarized the news (via Kotaku):
The good news: the slide pad is optional and compatible with more games than just the much anticipated Monster Hunter 3G. It even works with the upcoming Resident Evil: Revelations, Metal Gear Solid 3D: Snake Eater, Kingdom Hearts 3D, Ace Combat 3D Cross Rumble, as well as Dynasty Warriors VS, according to Kotaku. Since Monster Hunter 3G is only releasing in Japan (for now), the device is heading to just that country this December, with no date set for an American arrival yet.
Officially dubbed the 3DS Expansion Slide Pad, what do you think?