If Steam itself goes bankrupt, that decision is not up to Steam, it's up to its creditors and the bankruptcy court. It's not a credible promise for any US corporation to make, regardless of its trustworthiness.

Ah cool, so an alleged promise made to one user makes it all OK and we should stop worrying and just buy more.

Even if Gaben "money drives the community" Newell did make that promise and was sincere, he's going to be gone in a couple of decades at most and likely not in control of Valve before that.