Will a door rubbing on the carpet cause excessive wear?
Depending on how much of the pile is being rubbed it could wear off some of the pile. It will also cause more wear if it's a berber type of carpet or some other type of looped pile where the door could wear off the top fibers.
What it will cause, especially on pile carpets is a 90 or 180 degree arc in the carpet where it rubs. However if it's not a deep rub it should look better after vacuuming or shampoing.
Bottom line is try to minimize the amount of contact between the door and carpet by trimming the door so it just contacts the top of the pile and you should be fine.