The digging in Osaka was all infrastructure. At least from the vantage points we were shown. 1. I would highly doubt that the MK building could support the weight of 2 full fledged rides, however I wouldn't rule out an additional experience of some sort (like an Olivanders / Savii's / VR smaller scale experience, thing, maybe meet and greet?) 2. The land is operated by the park, they would not build studio facility in the park. 3. Remember that Yoshi queue in Osaka is SLIGHTLY using the MK building, so we have that extra space to justify. My best guess is it's either park offices (since the lower lot has been wanting new offices for a while), or a small retail / experience venue if it is in fact within the land.