9to5Mac is reporting that Apple Retail Stores are taking delivery of new fourth-generation iPad models with LTE cellular (though not the iPad mini), but they have not begun sales of them yet.
Apple has begun stocking its U.S.-based retail stores with LTE versions of the fourth-generation iPad. The product is not on sale yet, but they could go on sale at anytime. Stores have been instructed to wait until word from corporate comes through to begin sales.
Cellular-capable iPad mini and 4th-gen iPad orders are expected to be delivered to US customers beginning on Thursday and Friday of this week, and it's likely that retail store sales of cellular-capable fourth-generation iPads and iPad mini's will begin on Friday. Recently, Apple has generally launched iOS products on Fridays.