No, the brass will not change shape or shrink from that heat. What you seem to be describing is what normally happens after sizing . . . it's called "spring back". Depending on how work hardened the brass is the more spring back will occur and the sooner it will occur. Allowances for this spring back needs to be made for those who try to be precise with their neck tension when they get around to loading the cases. To avoid this issue you have with the Lee trimmer, you'll need to get a larger expander ball or a smaller pilot for your trimmer to accommodate this spring back, depending on what you're trying to accomplish.
The 140°F temperature doesn't do anything to the brass . . . unless it's left at the temperature for many many hours, then it will have some level of annealing to have taken place (made a little softer).
Of course, if you're not already aware, brass will expand or contract depending on it's temperature, where the brass will be larger or smaller depending on its temperature. But, to be able to measure the change in size, there has to be quite a large variance between a cold temperature and hot temperature.