TPS6206x - ambient temperature above 85 C

Nothing as long as the junction temperature remains below the recommended maximum of 125 C.  At these high ambient temperatures, it is more difficult to remove the heat from the device and keep the junction temperature less than 125 C.  This is the key parameter--junction temperature.  At junction temperatures above 125 C (the absolute maximum rating for the device), the IC could be damaged.  In typical applications, a 40C rise in the device is common.  Thus, the ambient temperature is recommended to be below 85 C to keep the junction below 125 C with a 40 C rise.  If operation above an ambient temperature of 85 C is required, special care should be given to the thermal layout of the device and the output current may need to be reduced.

See also this design note: http://e2e.ti.com/support/power_management/non-isolated_dcdc/w/design_notes/1869.tps62xxx-operating-above-recommended-maximum-ambient-temperature.aspx