This ain't no 3D remake; it's just all the content from other versions of the game on the 3DS.
Cave Story is getting another release on the 3DS, though this time it appears to have more in common with the Steam version Cave Story+ than the 2011 3DS remake.
This version, unveiled in this month's Nintendo Power, will include a laundry list of modes and features, including jukebox mode, adjustable controls, Boss Rush, Curly Story, Hell Time Attack, Wind Fortress, Nemesis Challenge, and more. It will also add a widescreen presentation and 3D effect.
However, it looks like the DSiWare version, which is out in North America, may be removed from the eShop before this comes out. It will remain in the DSi Shop, though.
We've reached out to Nicalis for confirmation about the game's contents and planned release window. We'll update this as we get more info.