Feature Set in Excel

Microsoft provides a new version of let's say Excel every two or so years. Every new version comes with a set of new features as well as bug fixes. I'm aware that it necessary for MS to show some new features from a marketing point of view. This question does not point towards the reasons MS does this.

I'm wondering: Is there a point in time when more than 95% percent of all excel users had everything they needed? Is the increasing number of functions in every new version making Joe Average less productive simply because he can't oversee the increasing possibilities?

Certainly somebody else thought about this issue. And maybe came up with a chart of "number of functions" vs. "average productivity", with a set of curves representing certain Excel versions, finally showing the sweet spot?

P.S.: I'm not sure if this question or a something similar is already discussed in political economics, or it so uncommon that it can "only" be seen on xkcd.