The just-announced new iPad will be offered in an LTE version, marking the first time that Apple has offered a true 4G-enabled product. Of course, LTE support requires carrier partners with LTE networks, and both Verizon and AT&T are predictably on board — both with their own versions of the device (they've got different LTE networks that use different bands). In Canada, Rogers, Bell, and Telus will be offering it as well.
Of course, there'll be 3G fallback for when you need it; LTE is still in fairly limited deployment, so this'll be the primary mode for many users. On HSPA+, the new model supports both 21Mbps and 42Mbps dual-carrier modes — no slouch, needless to say.