> cheap and easy to actually keep bathroom surfaces sterile
I think that flatteringly overstates modern human abilities: Almost every surface on Earth either has life on it or is about to be get recolonized in short order. (Often after we did some temporarily-effective thing involving brute force radiation or unusual heat or volatile chemicals.)
At best we'll end up with almost-sterile bathrooms that we're OK with because life that is both process-resistant and dangerous hasn't popped up yet.
> We'll adapt to our increasingly sterile bubbles and become increasingly vulnerable to Earth's microbiome.
There are two flavors to this that I think really need to be distinguished, because they lead to very different experiments and recommendations:
1. "Hygeine Hypothesis" - "Our immune systems need to be toughed up by winning battles against actual pathogens."
2. "Old Friends" - "Our immune systems need additional calibration by harmlessly interacting with the suite of benign things we co-evolved with."
The former suggests that a certain level of (literal) inner turmoil and danger is required, whereas the latter suggests that it's a much more general issue of micro-ecological diversity and no pathogens are needed.