I disagree with the high level equilibrium explanation. The Chinese economy was always large and had cheap labor - but didn't stop technological innovation before, due to the threats from external invaders (Europeans and northern nomads during the Ming, and northern nomads during the Song) and new ideas/products brought in by traders. In my guess, what really put an end to technological innovation during the Qing was the final conquest of the remaining northern nomads, the stabilization of the tribute system and the settlement of the border with the Russian Empire. There was no longer any motive, economic, diplomatic or military, for innovation.
I do not think that this phenomena will occur again - today's northern nomads are simply replaced by the rest of the world, and global economic competition has made it such that you can't stop innovating, or you'll fall behind. The Mongols are at the gates (mentally), permanently, and that sort of pressure - the desperate drive to survive - will ensure Chinese moves innovation forward.