99% of firmware updates DO NOT affect calibration. There is always some misguided manufacturer who flubs this and resets everything back to defaults, but, in general, the location the calibration data is stored is completely separate and protected from the area where firmware resides (and is uploaded to).
So 99% of the time you do an update, if you think you're seeing something different, you aren't.
Depending on how new your model is and whether it has had previous firmware updates or not.... your calibrator will not necessarily know if updating the firmware will wipe out the calibration. TVs that have more frequent updates and that are more popular among people who have calibrations performed (Panasonic and Samsung seem to be the front runners for flat panel calibration by a fair margin over other brands) will be more likely to have been closely scrutinized (and perhaps measured) before and after a firmware update. Less-often calibrated brands (Sharp, LG, Toshiba, etc.) are less likely to be "caught" wiping out calibration settings after firmware updates just because fewer people/owners, are looking for that problem.