As you're no doubt fully aware, Apple has announced a new iPad with support for 3G and 4G LTE networks for Verizon and AT&T in the US. Sprint, however, was left out in the cold. The lack of support was not unexpected, the iPad 2 never came to Sprint despite the fact that Apple does make a version with a CDMA radio. However, the iPad 2 predated the deal to launch the iPhone 4S on Sprint, so it wasn't entirely crazy to think that the new one could have made its way onto the carrier. Sprint is also working on launching its own LTE network and has even has LTE phones announced for later this year, and obviously LTE is an important feature on the new iPad.
So what happened? Sprint's not saying, telling Fierce Wireless only that "Sprint is not a carrier for Apple's iPad products. [...] We have nothing to announce at this time." Still, it's not hard to read between the lines. Sprint had to put out a significant amount of cash and guarantees to Apple in order to secure the iPhone 4S, a device that required minimal work to get on the carrier. LTE radios, however, are a different story. Apple already needs to make separate versions of the iPad for AT&T and Verizon because of their different LTE bands, Sprint's LTE network would likely require a third given Sprint's spectrum for LTE.
More to the point, Sprint's plan to go nationwide with LTE is made up of set of partnerships held together with duct tape and baling wire. That plan also unraveled more than a little when LightSquared fell out of the picture. The situation makes launching a Sprint LTE iPad a somewhat risky proposition for Apple and Sprint is certainly in no position to offer another massive outlay of cash to smooth things over. Apple obviously wants to sell as many iPads in as many places as it reasonably can, but it's hard to blame the company for giving Sprint the cold shoulder.