"Every cloud vendor in the world telling you off" is a particular threat model only usually encountered by literal terrorist groups, torrent sites, Sci-Hub... and now right-wing filter-bubbles.

In this case, Parler will need to either build all their own infrastructure or sign up with some really skeevy second-world hosting sites. This, interestingly, means being hosted on the same servers that host actual terrorists like Hamas; if they intend to remain a legal corporate outfit their lawyers will probably have some very strong words about using such services. Building your own infrastructure is expensive, even without the particular threat of just being Parler. Notably, net neutrality has been dead in the water ever since Trump took office, so anything high-value becomes extraordinarily expensive fast.

I doubt other sites are going to face this same problem in the future. Parler's problem is not that they're on the "wrong side" of a political debate; it's that they deliberately aided and abetted the planning of literal insurrection. Providing any sort of service to them is a huge legal risk to your enterprise now. If the bar for technical deplatforming was lowered beyond "technically legal", you'd see the market for alternative infrastructure providers open up, because those are customers that AWS/Google Cloud/Azure are no longer serving. AWS can only "get away with" deplatforming Parler specifically due to the legally risky nature of working with them.