I have have three XC6SLX75T devices that have failed under random vibration. The balls have separated from the package in the corners. The device is supported with gap pad between it and the heat spreader. The board is very well supported and analysis predicts .001" of deflection in the area of the device. A hand calculation recommends no more than .006" in that area so I'm well within that. I can't find any information on vibe in the data sheets.
Typically, in environments with vibration (like rocket launches, automotic, industrial), conformal coating, and other mechanical means are used to help secure the devices. Talk to your assembly vendor on those options.