The process of advancement in audio reproduction is more of a random walk than a straight line jog from better to best. If you examine the product history of companies that have been in the business for a significant amount of time you will see numerous changes is design philosophy and many "dead end" product lines.
You should also give some consideration to exactly why a company comes out with a new product. Frequently it's due to supplier issues. If a certain tube is no longer being produced, then an amp manufacturer will have to change the design of their amp. The new amp could in some ways be better than the old amp, but that raises questions about why they picked a different tube to design around in the beginning.
Despite what I say, eventually someone will release a Signature Reference Statement Mk3 product and some audiophile will immediately feel the need to upgrade from their beloved Mk2 version.
You should also give some consideration to exactly why a company comes out with a new product. Frequently it's due to supplier issues. If a certain tube is no longer being produced, then an amp manufacturer will have to change the design of their amp. The new amp could in some ways be better than the old amp, but that raises questions about why they picked a different tube to design around in the beginning.
Despite what I say, eventually someone will release a Signature Reference Statement Mk3 product and some audiophile will immediately feel the need to upgrade from their beloved Mk2 version.