I don't think 37signals is a very strong example that this could become a trend. They are in the goldilocks zone where they're big and stable enough to save a lot of money with self-hosting, but not big enough that they can negotiate meaningful discounts with Amazon.
In reality cloud is too convenient, and the tradeoffs for self-hosting just don't make sense for the majority of companies. The talent to run your own servers with modern HA and reliability expectations has largely been consolidated into the giant cloud providers and other large companies at this point. As much as I think a lot of cloud is wasteful and more diversity would be beneficial, I don't see any meaningful change to cloud dominance on the horizon.
In reality cloud is too convenient, and the tradeoffs for self-hosting just don't make sense for the majority of companies. The talent to run your own servers with modern HA and reliability expectations has largely been consolidated into the giant cloud providers and other large companies at this point. As much as I think a lot of cloud is wasteful and more diversity would be beneficial, I don't see any meaningful change to cloud dominance on the horizon.