Just went to change my account from the Motorola Xoom that I have on 4g to my new Ipad next generation and they told me that I only had a choice of 2 much more expensive plans. Did I miss a notification from Apple or Verizon? Ouch.
I would think that your Xoom plan was a special deal to help get rid of them. To my knowledge, you should have a choice of four plans. If you have something like a 3 Gb plan, you will have to go smaller, or get a 5 or 10 Gb plan.