Quote - Yes, it is shrinking.

Why?

In the beginning there was only Poser.
Now there are more and more apps coming into the competition, cutting into the Poser user base.

All depends on what do I get for my dollar?
End user friendly?
Bug free and crash proof?
And yes, content creater friendly too?

The market is driven by its customers.
And sometimes customers look at the competition.

The best way to keep Poser on its rails is to release the next versions with more native high quality content and become as end user friendly and as bullet proof as possible.
Just my 2 cents.

Your argument presumes that there is a finite number of Poser users that isn't growing.