At approx. US$15 million, it can be seen as a prestige acquisition by a Chinese company for not a large investment. I would think that nominally, the parent company would do as little as possible (at first) to disturb the brand's position within the market place. Stax is a known entity, highly-regarded and commands a premium for its products. The parent company using the Stax brand to market a $30 iem dilutes the brand and makes the investment worthless.
I would think that the Stax manufacturing would likely stay in Japan, since a move away from there to a mainland China manufacturing site would be poorly received in the market, regardless of the actual quality of the factory, and result in a loss of asking price. What would likely happen is that the technology and manufacturing processes will be exported and used to create a more center-market brand to compete with Audeze and Hi-FiMan.
Someone in the mainland has looked at the market numbers and seen that the biggest growth in music home-entertainment is in headphone and personal systems, and they want to tap it.