The way they did the air cards was force new plan
I have a 3g grandfathered unlimited air card plan. If I get Verizon to subsidize my new air card and sign onto an new plan I lose my unlimited status. The answer was to buy a new one at full price and keep my unlimited plan. Problem with that is, they don't sell a 3G card any more. I can get one off ebay or another source and have them activate it on my number if I have to. I was going to buy a new 4G air card at full price and enjoy the benefits of the faster speed, but Verizon said they would not consider a 4G device part of my 3G plan, so if I wanted 4G, I had to sign onto a new plan and lose my unlimited data plan.
Roll forward to my Verizon Motorola droid, I was able to upgrade my device on a phone plan to a 4G phone, and keep our family unlimited data. This seemed to be a good deal. No extra costs, keep unlimited data plan and get 4G speed. The problem with what is proposed, is not all 4 phones on our shared plan is 4G. The primary phone on the plan is not 4G. I wonder if it switches to 4G will the entire plan lose it's unlimited status? Since I'm sure all new phones will be 4G like they did the air card, it may be check mate on the Verizon unlimited.
I have a couple of nephews who use a month to month plan, and have unlimited talk, text, and data for $45 a month. Maybe this is another option for some.