It's interesting, because Visicalc was originally dominant. And then Lotus 1-2-3 was dominant. And now Excel is. Each could read the format of the previous one, but improved features/performance. The switchover appears to be related to platform changing, to IBM-PC, to GUIs. Which is how it usually goes. One would expect an Excel-slayer to emerge from a platform that replaces Windows - such as the web or the iPad (or some new GPU/many-core architecture that gives us speed equivalent to extrapolated clock rate increases if they hadn't stopped at 3GHz about 10 years ago), if it somehow invades the enterprise. i.e. a Windows-slayer.

http://dssresources.com/history/sshistory.html --- http://en.wikipedia.org/wiki/Spreadsheet#History