It won't give you a warning that the sensors were moved.
If you get a low pressure situation, it will still give a low warning, but will be indicating the wrong location.
The sensors will still give a reading -- but the truck won't know the correct location of each the sensor unless you go through the relearn process.
eg -- if you moved both rears to the front, and don't re-learn the positions, then the display will show the pressures of the tires (that are now on the front) as being on the rear.
You can verify this by pumping up a pair of tires by say 5psi and seeing how the higher pressure shows up on the display.