It's that 3rd point, the reintegration into the core, which I see as untenable.
And what constitutes the core, anyway?
Learning things about the language that only fluent speakers can know means the language will be improvable in ways the original designers couldn't have anticipated (or they would have). Therefore change is inevitable. What's not likely, though, is that the change will keep the language unified, even backward-compatible. Something along the way (an imperfection in the original design) will become broken when the change occurs, and this is unavoidable.
For those who want to learn a language that will never change, pick something like Sanskrit or Middle Egyptian. Languages MUST change to stay alive.
stevo