I’m always suspicious when someone says “this time it’s different”… :-) I agree that there is indeed a risk that consumerism will kill capitalism, because it will lead to the ultimate depletion of scarce natural resources. The question ‘Then, what?’ is inevitable — if that does indeed happen.
But won’t market forces counteract much of this? We’ve had peak oil for decades, and still we can happily drive about (although our cars consume far less fuel than they used to 50 years ago). As resources become scarcer, they become more expensive, and that depresses demand, encourages frugality and/or recycling, and acts as an incentive to dig up or drill for the resource in more expensive places.