Thank you both for the responses and recommendations. When I got the iPhone 4 I needed to upgrade iTunes and the OS on my older 2006 model Mac, as well as increase the RAM. So before looking at a new iPhone I am trying to determine if I will be able to use iTunes on my existing desktop with the new phone's iOS8. Or if I will need a new desktop as well.
I will continue to research 11.3.x compatibility with iOS8.