The real question is why doesn't Smith Micro focus on making Poser support for modern figures more user friendly? At the end of the day content creators are going to create for whatever there is a market in.Though I'm sure V4 will continue to see support for a while yet as well loved as she is/was. But it is inevitable that support will slow as more and more customers adopt the newer Technology. V4 was released in 2006 that's 9 years ago, V1 came out in 1999 thats a 7 yrs gap between V1 to V4. 

It's probably not helping the market that Smith Micro has a fairly hefty entry price with Poser 2014 nearly $500 and a purchase of V4.2 is nearly $20. Whereas Daz Studio is free, Genesis 1 and 2 bases are also free. WIth that in mind as the market expands less and less people will be using V4 and possibly even Poser. This not only affects the customer base but emerging vendors who are more and more using DAZ Studio as their application of choice. Also there will be a percentage of people who will decide its time to upgrade from V4 to the newer figures. Ultimately modern figures are where the future of the market is. And Nostalgia will not be able to hold back the market ultimately.

“You never change things by fighting the existing reality. To change something, build a new model that makes the existing model obsolete.” ― Buckminster Fuller

“There are many ways of going forward, but only one way of standing still.” ― Franklin D. Roosevelt