This is what bugs me about both quantum computers and commercial fusion power. There's so much talk about how it's just inevitable and will happen soonish, but a lot of the evidence suggests, in some cases strongly, that it might not ever be possible.
I find it weird how bleeding edge research, at the very edges of both physics and engineering, is treated as though it's a market development about to drop. Possibly a consequence of pure R&D having all but died? Getting funded requires pretending there's a business plan for what you're working on?
There's no strong evidence of impossibility. For quantum computers to be impossible at scale we need new unknown physics. Fusion requires lots of engineering. And before those engineering efforts would show practical impossibility or impracticality, there can't be strong evidence.