Oh come on now. It's like they said in an article I read recently... the world has learned about Ponzi schemes, and now everything is a Ponzi scheme. At these macro-economic levels, there can be no talk of "Ponzi schemes". The economy is not an investment vehicle, it's a huge, loose, and fantastic agreement that enables all of us to get far more (in terms of technology, resources, comfort, life expectancy, health, ha…
He isn't saying Capitalism isn't the best system, he's saying (precisely as you have said) that it won't last forever in it's current form. That we should start thinking about the repercussions of our current model so when this model becomes unsustainable, we'll already be transitioned into the new.
I certainly see no problem in thinking about our future instead of refusing to look ahead because... well it's going so well right now we shouldn't rock the boat.