this development, in my opinion, will be tied to
economics

Jackie,
Whilst I agree that economics are a factor, and much as I love the potential literal truth of "money talks" , I think adoption of a language is dictated by far more subtle factors than material wealth. You'd have to ask "what's the value of people taking the effort to learn the language", and the higher the value, the better the incentive to learn the language well (or rather, according to the standards of the most valuable dialect - heck, this gets like swallowing a fur-ball).

The value of a language can be dictated (ouch) by such features as:
* the culture to which you can gain access (both in terms of technology and art),
* the ideas you can express (e.g. if Inuits have several words for different kinds of snow and a new Ice Age sets in, Inuit could be a valuable language),
* good friends and work colleagues who use the language (especially if you take a fancy to any of them ),

etc...

In other words, there's a whole bunch of "soft" criteria that come into the equation. This is appropriate if we see language as more organism than construction (mea culpa, folks).

Following on from that - and this is mentioned in the article - it's almost impossible to define an English speaker except by subjective means. Even if you could get people to do an official test, what variant of the language would you measure against? You'd probably have to pick a time as well as a place!

I'm sure that in a few years' time I'll have trouble understanding what my kids are saying to their friends, that's my opinion. Still, if I give 'em a dose of (by then ancient) AWADtalk it may serve to return the compliment.