The Mi Max series offers large devices with hefty batteries, so it's no surprise that the next device in the series, the Mi Max 3, will turn the dial to the extreme, with a larger display, bigger battery, and a SoC upgrade.
https://www.notebookcheck.net/Xiaomi-Mi-Max-3-to-feature-7-inch-display-5500-mAh-battery-Snapdragon-660.274350.0.html
660 is unlikely and you're leaning on 630. Then, I'm betting on 626 and I'm willing to bet in quite far future 630 on Mi A2 or Mi6X (because the other 2 Android One devices are using 630).