Alas you are only partially in luck with poser. As of version 12 you CAN still use the older figure (v4 etc.) but you are wasting a lot of functionality (some wil disagree with me here) since they are using figure without weight mapping at least if you want to use clothing etc form the same era.

Poser comes with LaFemme as it;s flagship figure these days. She is weight mapped and includes SOME later technology. Older content can be used for her if you use the fitting room and the set up room to convert the rigging. It's not easy but it's there. Some people seem perfectly happy using the older figures and content. 

There is a male figure L'Homme I don;t think he has a free version sold with Poser? Since he's built off of modified LaFemme rigging her has most of her tech.

There is a major amount of content for either of them yet but it is growing pretty much every day, and there as some very gifted content makers worhing hard to provide more.

Don;t know if this helps. If it does great!

Have a great day