you have Verizon's $29.99 unlimited data plan, you'll be able to keep it after July 7.
You'll also be able to keep the $29.99 unlimited plan when you upgrade to a new phone.
If you add a line to an existing account, you'll not be able to chose the $29.99 unlimited data plan.
If you're a new customer between now and July 7, you'll still be able to choose the $29.99 plan. I just copied this from verizons web site