This is my opinion based on my experiences.

I was a dedicated longterm DS-only user for years.  DS4 convinced me to make the jump (and the investment) to Poser.  I figured if I was going to be forced (and really, unless I wanted to severely limit my new content aquisition, there really was no choice at all) to learn a completely new program and workflow then I'd go with the program that had adequate documantation, a reasonable update/upgrade path and more useful stock tools.

I do not regret having spent the money and making the switch.  At all.

As for the Gen4/Genesis figure question, I'd be willing to say that Genesis has not and likely will not dominate the market (except for at the Daz store). Its lack of compatibility with programs other than Daz Studio 4 (and serious lack of backward compatibility with previous versions of Studio) truly limit its usefulness to anyone but Daz Studio 4 users.

The majority of the people I associate with don't care for Genesis and I'm really with them in not having any interest in the figure or products made for it.  I personally will not be investing cash or hard drive space on the Genesis figure.  It offers me nothing I want that I don't already have in my current arsenal of humanoid figures.