It should be self explanatory. There are no hoops to jump through to get V4 to work in Poser. There are many users who do not want to use anything but Poser, and many of them haven't upgraded to P9+. 

(eta: x-posted the above w/ coleman)

 

But there have been several sales of P10 and PP2014 with drastic cuts on the price, making it very affordable for those who weren't necessarily able to upgrade right away before. So that will naturally have broadened the user base of P10. There are also other websites that still have P9 and PP2012 for sale, and have at times cut the prices rather drastically, again increasing the userbase. 

The difference with Poser is that you have to pay for your upgrades, and a lot of people don't upgrade right away. It takes them a good while to do so, either due to their finances or just not seeing anything that really stands out to them innitially. The economy hasn't been all that great for the last several years, so a lot of people can't afford upgrading software when they have other things in RL that are much more pressing. 

So this is going to affect how well a new figure that requires that software is going to be recieved innitially. Vendors that attempted to incorporate the newer features into their content back when P9 was new, that are not supported by older versions, were likely not all that impressed with their sales early on so they gave up on it and went back to building content that was compatible with the last 10 years of Poser versions. Today their sales should be stronger for content with those features because there are many more users that have upgraded since then. 

I don't think Dawn is a doomed figure. She still has a loyal following who are supportive of her development and her developers. But like Coleman said, it's going to take time for that appeal to grow. HW3D are still developing for her, so they must be making enough from her currently to consider it beneficial to continue. 

 

Quote - Dawn's selling point of being the ONLY figure able to be used in Poser 9+ and DAZ4+... that is her strongpoint... in theory. DAz users probably could care less about her. Dawn is really a sell to the Poser crowds... (1) and (3).

My Michelle over at RDNA is backwards compatible with both Poser and DS, so Dawn is not the only figure.