If your computer runs 4.7 it should run 4.8 without a problem.  3Delight rendering is still there, there is just an option to use IRAY if you want to.  That said, IRAY should also work, it uses the CPU if you don't have a compatible graphics card.  Whether you use Genesis 3 is up to you, but the base is free.  Nothing saying you can't stick with Genesis 2, it's going to be around for a while.