The Speculation: When Google released its Nexus 4 phone, users were shocked to learn that the device did not support 4G LTE, the fastest type of mobile network. To avoid dealing with carriers and building carrier-specific versions of its handset, the company decided to go with simple HSPA support, a decision Android head Andy Rubin called a "tactical issue.". Despite Rubin's comments, some believe that Google will eventually offer an LTE version of the Nexus 4, because it provided carrier-specific LTE versions of its prior-gen phone, the Galaxy Nexus. The Nexus 4 even has a disabled LTE radio inside of it, though this radio can only support a handful of bands that most areas of the U.S. don't use.
Why It Won't Happen: With the Nexus 4, Google is trying to make a point about its independence from carriers. Users who want a nearly-identical phone with LTE can already buy the LG Optimus G. However, not including LTE on phones is a poor long-term strategy. I wouldn't be surprised if Google's next handset, rumored to be the Motorola X, had LTE that worked with at least a couple of the major U.S. carriers' networks.