|English is going down even in the USA|
One of the truisms of investment is that you invest in where the biggest growth is, this would benefit languages like Russian, Spanish and Portuguese. The problem is that this does not help any of the other languages including English. So there is a need for a different approach.
Considering the formulated approach of leaving local things to chapters, the WMF can invest in technology and approaches that are neutral to languages but promote growth. A truly multi-lingual Commons, improved usability for MediaWiki and Commons, tools that identify demand..
There is only one aspect where language targeted investment makes sense; this is where a level playing field is established. This is where we fix issues that prevent a language to be properly expressed on the Internet.