Speculation On 2019 Issues?

They'll still need new stamps for the new:

Additional Ounce 15¢

Two Ounce rate 70¢

Not necessarily. If existing stocks of the current non-denominated stamps that meet those rates are sufficient, there is no pressing need to issue new ones.

Logic says you are correct. But if so, why do we have so many different one ounce First Class rate stamps when we really only need ONE such stamp? And they keep issuing new ones at a rapid rate. With the advent of the Forever concept, we'll never need a new stamp; they can just raise the selling price as the rates increase. They'll be doing it starting Jan 27 for all existing "Forever" stamps.

As far as I know, there is currently no 15¢ stamp in the USPS system.

They have had the CA Dogface stamp for two years now. It was supposed to have been issued in 2017, but the rate for non-machineable letters never changed (and still won't in 2019). Nonetheless, it is announced for issue in 2019.