It appears that the USPS is heading down the path of making all commemorative stamps with the Forever designation, meaning they are good for first class postage at whatever the prevailing first class postage rate is at the time they are used. If you follow the philatelic press, you know some people are questioning and challenging the USPS move.
Challenges aside for the moment, suppose the USPS is successful and continues issuing Forever stamps. Does this mean an end to definitive stamp series like we’ve seen in the past? Maybe.
We’ve had a number of delightful definitive series over the years. The 1938 Presidential issues (the Prexies) are a popular set. The 1954 Liberty series is an interesting series because of tagged and untagged issues (among other things) as the postal service moved towards automation. Even the Prominent Americans from the 1970s are being studied.
Definitive issues typically have a similar series of designs. The varied denominations were used for a wide variety of postage rates. These stamps were used over long periods of times, sometimes two decades or more, before being replaced by the next definitive series.
With the move to Forever stamps, there is no need from the public for 1˘, 2˘, or 3˘ stamps to make up the new postage rates. And over the last 20 years or so, the USPS has installed computers and postage meters at even the smallest of post offices. It used to be that small post offices didn’t do enough business to justify installation of a postage meter machine. Now, everyone has one as the USPS moves to full automation. So who needs odd denominations of stamps for special postage rates?
Do we need definitive issues any more? Not really. The need for them has almost dried up.
Will the USPS stop making definitive stamps? I don’t know. But if they continue with definitive stamps, I expect the set to be much smaller sets. Past sets typically had 20, 30 or more stamps per set with a wide range of denominations. I expect modern definitive sets to contain 5 or 10 stamps per set with denominations for things like double and triple weight first class letters, non-machineable rate letters, and things like that.