The broad consensus in the physics community is that quantum computers are in principle scalable (using either software error correction or, speculatively, stil

The broad consensus in the physics community is that quantum computers are in principle scalable (using either software error correction or, speculatively, still-hypothetical topological quantum devices). As for anything, there are of course still some naysayers. (Gil Kalai, mentioned in a sibling comment, is not a physicist and does not have a proposed physical model behind his objections, but his intuition could be correct.) If some undiscovered law of physics forbids it, that would be amazing! A more likely obstacle, though, is that it is just a really hard engineering problem.