i haven't gotten all the use i could have out of V3, let alone V4.  i mean, texture sales, that would be an issue.  that said, V4's been out a long time, and the most popular textures for her right now are very conventional.   i think quality work for the latest version of Vicky that worked in Poser would remain popular.

Antonia seems pretty high quality and has pretty good support for a figure that isn't even to a 1.0 version yet.

i think it would be a case of adapt or die for the community.  and i can't say which way it would go. but if the community died off, then death would be very slow.

i suspect that even if no new versions or figures came out for Poser, there would still be a pretty significant community and market for some time to come.  i mean, i keep seeing people complain about losing the P4 renderer.  the main reason we get new figures is all the cool new stuff we want to buy that works on them.  right now there are nearly 6000 people on this site, and most of numbers seem to be from the Poser community.  the Vue forum is more active than the DS forum.   Poser users stay pretty well behind the leading edge of Poser use or even just Poser versions.  the bulk of the market runs on users who buy on impulse and want to spend no longer than an hour waiting for a render.  look at the top viewed, rated, and favorited images. you'll see lots of incredible technique, but most of it is 2D, not 3D.

i think anyone who wanted to try to make money off the exceedingly disgruntled Poser users would have several years to do so.  the more entitled, demanding, and emotionally volatile aspect of the community would actually work in the favor of independent development for once.  if DAZ completely dropped Poser support, or even made flagship figures that didn't work very well in Poser, it would open a major door to independent developers.  i mean, can you imagine if there were no DAZ males for Poser when Apollo came out?  Anton said he sold over 1000 copies during his release sale.   considering how many independent figures i already have in my runtime, my guess is people would be scrambling to fill that niche.

i think we'd have a chance at breaking our DAZ dependence and seeing the emergence of stronger independent developers.  this community isn't big on change as drastic as switching to DS, and even more importantly, mostly doesn't need it anything Poser 6 can't do right now. if tomorrow all versions of Poser were updated to use Vray as a renderer, people would still render without shadows.