How about neither ;D
If MAME doesn't change its versioning, after 0.999 comes 0.1000

Realistically, some one-off prototype chesscomputers are unobtainium. Like that Boris robot that looks like a sewing machine. But before we reach that close to the end, there's still plenty left to do.

I guess it's similar to chesscomputer collecting? Noone has a 100% complete collection, prototypes and tournament machines included.