PQD will not specifically affect my purchases -- if UA has a competitive fare to a place I need to go at a time I need to go, I will probably still book it preferentially. However I will be much more attune to what is available from the competition and book more on the basis of schedule than I do now. Currently I take inconvenient flights to get on UA sometimes. That won't happen anymore. Some discretionary travel will also be reduced or eliminated, as will roundabout routings that accumulate more PQM than a direct trip.
The net result of this will probably be a small reduction in spend on UA. Since I have only spent about $8000 this year, I guess the reduction will be less than $3000 next year, but I really can't predict.