I'm also a bit concerned about the "new monopolies" that could emerge after a PoW change. It may sound a bit naive, but - is there a possibility to create/fund an open hardware project for mining chips running the "new Bitcoin algorithm"? It's true however that major "chip foundries" are located in China, but there are at least some scattered around the world (mainly Europe and North America) which could step in for production.
I think it's possible. But, the competition with China won't gone since the cost to manufacture the chips is still cheaper on China.
Maybe manufacturing the chips in China isn't really a problem. Many companies from other countries manufacture their products in China, and they control that the producers don't "tamper" with the design of their products. If the Chinese manufacturer manipulated the product, the customer would be able to charge a penalty for breaching the contract and change the manufacturer. An "open mining hardware" project could do the same thing, ensuring no Antbleed-style backdoors are implemented - and such a backdoor would be very easy to discover, above all if the firmware is open-source.
Once Bitcoin and the mining market becomes really big, it would be perhaps no problem to install production infrastructure outside of China able to deliver similar production costs.