android is a linux based os.no one could charge you for an android upgrade.you can download any uncostumized versions for free from android.com.most devices are upgradable to newer versions.atleast one upgrade for your android devices are promised by google.commonly high end devices from famous brands will get updates very soon.while, most low end device's CPU's may be weak to work with the new versions of android!
Tablet or handset, make sure your device's hardware can comfortably run the newer operating systems before taking the plunge. Their resource requirements are much greater than their predecessors, approaching those of small laptops. Don't let external appearances distract you---display size doesn't matter. Neither does brand name. What counts is "under the hood"---if the specifications match the requirements . If they do, fine. There is no going back once done.