We technologically plateau because we reach technological limits. There aren't many important technologies not invented yet, things like nanorobots, compact fusion reactors or Dyson spheres are impossible. Whether AI is developed or not is irrelevant. After a century or two of stagnation, civilization runs out of resources and declines to pre-industrial level. This is our future.
1. We technologically plateau, due to humanities questionable ability to adapt to accelerating technological progression.
2. AI development is indefinitely disrupted; as it is likely to result in disaster.
All this considered, what's the most likely situation that could play out?