Android Lollipop is the new Android OS, and it is a good one. If you want to get a new Android phone, you will probably be happier choosing a one with Lollipop already installed.
This is not to say that phones with the older Android OS, KitKat, won't or can't be upgraded to Lollipop. Nor do I suggest they will be. It is a bit of a mystery. At some point, I assume, some older models will not be upgraded. One might assume that if you get a new model phone that still runs KitKat that you'll be upgraded eventually, but that is not 100% certain.
We are looking into a new phone, we use Verizon…