With TiWi-BLE module, the WLAN Transmitter Characteristics in data sheet is TA=25 degree C, VBAT=3.6V. Are these outputs warrantable within this range(-40 to +85 degree C) of the temperature?

Answer

The RF performance varies over temperature, and the datasheet performance is reported as typical at 25C.  There should be no WiFi module that can maintain constant RF performance over temperature.