The NeXTSTEP was called Quantrix. It's kinda dead, but not completely.
The OSS project is FlexiSheet. It's very cool, but needs some serious work.
Given the history of NeXT and innovative spreadsheet apps, I'd be a little surprised to see Apple come out with a plain ol' 2D spreadsheet. Maybe they use FlexiSheet as a foundation, or maybe they start fresh, but that's...