Its not just a port, its an official build so not based on anything but miui. On the less positive side, its out next week, not today. But not long to go.
It will be a true honest guess what gets ICS after those devices. My bet. The devices with most installs so the Defy, Desire and HD2. (All a guess, nothing official).
It would be great to see official miui support for the Sony Ercisson XPERIA X10 (has the same board as the nexus one). And if you look at the install counts, you could count the nexus one and the X10 together