The game's ESRB ratings page has been updated to include the new platforms, which now appear alongside listings for the existing versions on Wii, 3DS and Nintendo DSi.
Oddly, the listing also mentions ratings for PlayStation 2 and PSP. While a PSP release through PSN minis may actually be possible, the PlayStation 2 listing is more likely due to a broad classification for all Sony platforms.
ESRB ratings have a history of preceding official announcements by anywhere from a few days to a few months, though they nearly always pan out eventually.
Nothing has been announced on these new versions by publisher Nicalis, so there is no release timeline for the unconfirmed ports at this time.
Cave Story is currently available on WiiWare, DSiWare, the 3DS eShop and on PC. An enhanced version with 3D visuals also released earlier this year on Nintendo 3DS titled Cave Story 3D.
Watch a trailer for Cave Story below: