I still have my unlimited plan from the iPad 1 days. Switching from iPad 1 to iPad 2, I simply switched the sim cards. For the new iPad, I called them because I wasn't sure if the 3G plan will roll over to 4G. They said don't switch sim cards, just go to cellular in settings and log into your cellular account. It will ask if you are migrating from another plan. There will be a checklist with all their plans and they say "check the plan that resembles the one you have." the unlimited plan was in this list. The cellular plan will stop working on the old iPad, and will start on the new one.