5.5 licenses coexisting with 4.1 licenses

We are in the process of upgrading our VM infrastructure to 5.5 and was curious if all of our 5.5 licenses can coexists with our previous 4.1 until we get all the ESX servers upgraded. What I mean is if I add a 5.5 license will it overwrite or change the 4.1 licensing for the hosts? so we can add 5.5 hosts without worrying about licensing on the old stuff.