Actually when a game says it has that many Megs, I think it's in MegaBits not Megabytes (ROM is measured in bits not bytes). Where 8 bits == 1 byte. Doing some division (and yes I know it's not exact cause it's really 1024 bits per kB, and 1024 kb per MB), the 673 MegaBits for KOF99 translates into about 84 Megabytes, which makes sense, since the KOF99 ROM I play on my computer (I have the cart on MVS, don't flame me) is about 87MB. It can fit the game on the CD, it just takes a while to get it loaded off the CD. Theoretically a NeoCD game could hold a game with a cart Meg count of 5,200 (if the Neo MVS/AES hardware is still being used where we have 2D games (w/o FMV) that big on a cart, I'm going to invent my own chipset).
Personally I don't think that SNK will release any new CD games, since they really only seem to care about the MVS of late.
Actually, it may be possible to take the ROM of a game and using the technical info on the CD layout of a NeoCD game, that you could burn your own new NeoCD games (don't hold me to that though, it's purely theoretical <IMG SRC="smilies/smile.gif" border="0"> )
Peace
JHendrix