Licensing: Pools and Architecture Changes?

In the past, virtualization architects and administrators were told the best way forward is to buy as much fast memory as they could afford as well as standardize on one set of boxes with as many CPUs as they dare use. With vRAM Pool licensing this type of open-ended RAM architecture will change as now I have to consider vRAM pools when I architect new cloud and virtual environments. So let’s look at this from existing virtual environments and then onto new virtual and cloud environments. How much a change will this be to how I architect things today, and how much of a change is there to my existing virtual environments? Is it a better decision to stay at vSphere 4? Or to switch hypervisors entirely?