I see no reason to start collecting V9 either, even if I was strictly a Daz user.  Which I'm not. I export all of my Daz purchases.

I did so with the V9 basic and I see absolutely no way it's backwards compatible with anything prior, which it seems has been mentioned.  The rigging (total # of bones), UV's, you name it is totally different.  So any presets, Poses, etc., until some really clever person is able to come up with conversion utilities, is unusable.

Not to mention EVERY part (teeth, eyes, etc.) are separate morph naming, so it's doable for me, but is 6X the work.

So, unless it's an absolutely stunning, can't live without character, I see no reason.

Just my 2¢.