Interesting point:
At what point could, or should, an individual synthesizer, find its place, and not evolve; and remain in production?
In a sense, the recent close and almost-close reissues by Moog and Sequential are somewhat examples of this. But, the Moog ones are limited runs; and who knows how long the P6/OB6 will be around?
I see your question as: when will an analog synthesizer be like the piano, or the acoustic or electric guitar? I.e., could particular synthesizer attain stabilization in its evolution and stay in production.
The keyboard instrument surely is a funny category. When the finger isn’t directly connected to the string, the flexibility is vast. And accompanying that vastness can come a different form of detachment.
If one looks from a distant vantage point, all analog synthesizers are sufficiently similar, like all guitars, from a distance, are sufficiently similar. I suppose the significantly greater diversification of keyboard instruments also leads to a less focused production/consumption cycle.
But, likely just as relevant- the analog synthesizer is a function of technology. As the underlying, and relatively young technology continues to evolve, so will the instrument package.
In the case of the attempted one-to-one reissues, continued production is difficult with limited parts. By not being exact reissues, perhaps the P6/OB6 have the chance of staying around a lot longer.
Perhaps, and likely, the P12 was built upon technology that is being phased out, and replaced. And maybe, this is beyond Sequential’s control.
... And, the synthesizer innovators are ... innovators. In their essence. ... Others can manage the librarian tasks. As a musician improvises, an innovative synthesizer company, looks at now, past, tomorrow, assesses materials, trends, niches, successes, and whims, and instinct. And then innovates.