[[epistemic status: I am confident in the direction of core materials science that makes sea-steading possible, and it seems likely that sea-steads will become viable in the next 30 years. Much of what remains is a vague strategic outline for skirting the worst aspects of this coming shift to the sea. I hope to hear where I err, and what I've missed!]]
TL;DR - Sea-steading ("life on a floating platform") is held-back by fabrication and materials science. Following the trend of improvements in graphene, polymers, and robotic fabrication, AI-assisted design, then we can expect that sea-steads will become cheaper than residential land in the next few decades. At first, only mad lads will risk living on new designs - I expect a decade will pass before wealthy people migrate their precious stuff onto the waves. Once that happens, we have a chance for new governments: this has great value, as well as numerous risks. Chief among those risks is the destabilization of poorer countries, and the cascade of impacts from their slow collapse.
Time for another Federalist Paper
Only during certain brief spans within history could people write a new form of governance for themselves, free of constraints. At all other times, we trudge through political gridlock, or tumble from warlord to warlord. I see sea-steading as that next chance for new governance, and if we have 30 years before those settlements kick-into-gear, then now is a good time to start exploring which governments we might try!
I make the plea for a broad discussion on new governance, without the intention of building consensus! Instead, we should push thought in each different direction of the design-space with the understanding that there will be plenty of room at sea for HUNDREDS of new governments, soon. I see that diversity as more dynamic, creative, resulting in a system-at-large which is more stable than a "single-best-government".
Most important, however, is the fact that sea-steads will allow each different governance to be tested in reality. You vote with your feet, traveling to the island with the governance you prefer. And everyone you meet there is like-minded, committed to the success of their favorite style of rule. Migrants are gladly volunteers for the best scientific study of "which systems of governance work best, and in what ways?" We desperately need that data, to reduce risk of long-term cataclysm due to stalled/inept governance.
By exploring the broad space of governance ahead-of-time, we are better equipped to manage potential risks, and we have greater impact upon outcomes. The governing structures we might find are loosed from the normal requirements of "well, but how do we get that past the legislative bottlenecks and partisanship?" I hope to discuss the blank-sheet designs, as seeds for the consideration of future oceanic federations. I'll be responsive to every thread in the comments :)
The Cascades
We can reasonably expect a pattern of emigration, after years of testing in open waters demonstrate safety. First, some wealthy-ish folks (NOT the very-richest) will seek independence from their corrupt government, or they just don't like taxes and poor people. They already do this on real islands, so we can expect them to be the early-adopters who bring enough cash-flow to make sea-steading a viable niche. This group has been well-identified in previous discussions of sea-steading.
Next, we can also expect diverse religious and political groups to seek their chance for self-determination. They've done that throughout history, so this time shouldn't be any different. And, because the first to go will be the same people who are most devoted to that way of life, then we should expect the best possible results from their efforts. I do NOT mean to imply that they would succeed - rather, the opposite! Because those folks are most committed, then "if they fail, then we can be confident their system would ALSO fail with less-committed participants." We need that experimental data, and willing volunteers are the only people who can be expected to perform that test.
Additionally, once various forms of governance are tried, then the appeal to members of the professional class in less-well-run countries would grow. When they start moving to sea, I expect the Cascade starts.
While each of these groups will be small, themselves, their collective impact on poorer countries will accrue: 1) loss of tax revenue and business activity, re-investment from the wealthy fleeing, 2) brain-drain and stagnation of political institutions, as 'faithful' of each stripe leave for their chosen island, 3) poorer quality services in both business and government, slowing growth and restricting opportunities.
This last point is critical - when professionals flee the small dictators, that will cause failed states. I expect these refugee crises to accelerate that flight of professionals in those countries who receive them. As upper-middle wealth families try to sell-off assets, prices collapse, which hits the debt market backed by those assets.
I am not wishing that petty tyrants' states survive, yet the chaos is often worse for most. I still support sea-steading whole-heartedly, because of the chance to find which governments DO NOT fail! And, while I see the negative impacts I mentioned as the most likely outcome, I believe we can chart a different course - if we look widely across the design-space and plan far-enough in advance. How about you?