How many different variations on Cave Story do you own? It's been released on WiiWare, DSiWare and had a retail release on 3DS, but Nicalis isn't done yet, as it prepares another version for the 3DS eShop.
Nintendo Power (via Nintendo World Report) states the publisher is preparing an eShop version, but it's not a digital release of the 3DS retail version. Instead it's more like Cave Story+, with that version's Boss Rush and Wind Fortress modes plus widescreen and 3D display modes. It'll also feature a jukebox mode, customisable controls, Curly Story, Hell Time Attack and Nemesis Challenge.
One further rumble however: the DSiWare version of the game may be removed when this eShop release hits. That's no problem for European fans though, who still haven't got the DSiWare release.