Already, if you go to Apple's website to preorder an iPad, you'll notice that not all of them are shipping on the 16th anymore. The white 16GB iPad for AT&T has already sold out and had its shipping date bumped to March 19th. That's not a big difference, but a telling one nonetheless.
As we know, Apple only keeps 2 days worth of stock on hand and relies on projections to meet demand. It looks like Apple underestimated the demand for AT&T iPads with LTE, perhaps because AT&T's LTE network still pales in comparison to the coverage offered by Verizon's LTE network. Still, if you want an AT&T LTE iPad on the 16th, you may be out of luck, and be forced to wait a couple extra days, or just buy one with a black bezel.