Hi,
Re-polarity cannot damage the device, as there is protection.
As most CMOS ICs it has ESD protection diodes.
But they are designed for ESD pulses, only rarely occurring pulses of very short time.
They usually are not meant for steady currents.
In either case you need to keep on datasheet specifications. If it allowes to draw DC current of the ESD diodes, then you may do so.
Usually datsheets tells something like "port pin voltage must not exceeed VCC +0.3V" or so ... to prevent the diodes to become conductive.
Power down consumption.
As Brian mentioned the ports keep state at power down.
Check every IO whether you want it LOW or HIGH, don't let them floating.
I2C pullups
If the sensor is your only I2C device, then you may connect the pullups to the same port that powers the sensor.
Thus during power down the pullups are switched OFF, too.
Klaus