Such a shift will lead to a reduced level of price being deemed acceptable by the advertisers as payment to cable television channels for a lower quantity demanded of advertisements by them.
Furthermore, assuming that the supply curve does not change, it will result in a lower equilibrium point being attained which will ultimately lead to a reduced price being taken by cable TV channels for a showing of a less number of advertisements. This is because not all customers of the cable channel providers will have the PVR devices but only a fraction which can easily choose to skip commercials. The rest will still be viewing the commercials that are paid for by advertisers which is why a market for them will continue to persist. The PVR and accompanying facility will only be provided by the cable channel operators to their customers therefore if they are able to raise enough revenue via subscription fees that can offset the loss that comes from the reduced demand for advertisements by advertisers who will be put off by the devices as it will reduce utility for them.