Are U.S. Postal Stamps at the point of extinction?

Sending a stamped letter or package is still, by far, the cheapest route to take for its delivery. But, have we come to the time, when UPCs can take the place of stamps? Now, we can download and print certain UPC codes for package delivery, so why not the same for postage stamps? The U.S. Postal Service will save money, by not having to print as many stamps and waiting in a Post Office line may become non-existent. Question: Would it be feasible for The U.S. Postal Service to discontinue printing postage stamps, in lieu of home downloaded UPC stamps?