With just a single 16 GB model, of which about 11 GB are user-available, we'd say that user feedback will start pouring on Xiaomi's unsuspecting head honchos sooner rather than later, as Hugo Barra mentioned there was no place for putting a microSD slot inside the thin phone, on account of the dual SIM one. In retrospect, they could have gone with a combined microSD/SIM slot, as a few phones out on the market have already done, but that's another topic. All in all, Xiaomi said they won't be outing a 64-gigger before a couple of flash sales has gobbled up the 16 GB inventory that's sitting in the warehouse.
In other news about the Mi 4i, its protective panel is not Gorilla Glass 3, but is still made by Corning, so you can rest assured it is reinforced against scratches, bumps and light drops still. The Sunlight mode of the display, on the other hand, is always on, and you don't have to do anything to have it kick in when out and about on the beach. As for the Snapdragon 615 chipset, and the overheating reports from its first users, like Galaxy A7 and HTC Desire 820 - Xiaomi advised that this is the second production generation of Qualcomm's midrange processor, so heat won't be an issue.