But Does the existence of gen3 make gen2 or even gen 1 obsolete??…..nope.

Well if you're using DS then the whole thing is pretty clear cut. Use Genesis, adapt all other content to fit her, render in iRay and sleep happy.

It's when you're a Poser user or a cross app fan that things get a lot more troublesome. You can use V4 and live with the fact that almost all her content is obsolete and makes little use of current/next gen tech in DS or Poser. You can use Dawn and see her slowly fade into oblivion for lack of support and top tier content. You can use Poser natives or similar alternate figures and get even less support then Dawn. You can use DSON but get a figure that's a poor cousin of the one in DS. I suppose you could even go full 'commando mode' and start making your own sculpts or whatever but in that case you may as well move beyond Poser.

Or in short, what do you do if you want a modern, well supported figure but don't want to move to DS ?