Google Drive launching third-party add-ons program for Docs, Sheets
zdnet.com
zdnet.com
I'd gauge Google's ambivalence of commitment by the fact that seven years ago this sort of model could have been implemented. But it wasn't and there isn't some new technology that is driving it now nor is there a red blooded eeffort behind it. Avery has been providing label printing support for word processor software at least since DOS versions of WordPerfect.
Google's spreadsheet implementation is pretty much like every other alternative to Excel. It implements some fraction of the things which are easy. This makes it good enough and development stalls and people for whom spreadsheets really matter stick with Excel. Microsoft is often accused of missing trends, but spreadsheets are not one of them. Excel is the killer app that drives Windows sales for corporate desktop systems.
There's a reason it remains uncontested even by Google. Doing what Microsoft does with Excel is really hard...or at least the hard parts are.
The reason Excel is the killer app for corporate sales is that it is attractive to influencers (to borrow the term from social media). There are people on the executive floor who use Excel and often quite well. That's where the decision comes from. They don't want to fool with finagling their subordinates' TCP reports out of Scheme in a Grid, or Libre or Docs to crunch the numbers.
The power of Excel to drive top down decisions is why WordPerfect disappeared. Secretaries didn't choose Word. Their boss bought office because she wanted Excel and Word was part of the deal.
The fat part of the bat for Google is free as in hog pens and slop troughs. And that's the basis upon which they allocate resources. The development of Docs is so glacial that just about any expansion of the ecosystem is news. Even a whopping 50 developers.