Yes, there is more content being made for Daz these days, but there's still plenty being made for Poser, and plenty of it is for earlier versions of Poser. If you go to Market place home here, then click on market place at the top, then select "new poser" from the drop down, you will see the latest releases (and re-releases!) for Poser. Most of these will work in Poser 8.

Of course some figures have been designed to use features only available in later versions of Poser. So Hivewire products are designed for Poser 9 and later for example, and anything for the Pauline figure needs Poser 11. Some items have got textures for the Poser 11 render engine (Superfly) but most also have textures for the older Firefly render engine used in Poser 8

And remember, as long as you have your valid serial number for Poser 8 you could buy Poser 11 at the upgrade price, and watch out for sales of Poser.