Though the new iPad doesn't have Siri, it does have Dictation, which lets you dictate what you want to say to the email, notes, messages, and other apps. And like Siri, Dictation needs an internet connection in order to work, that's because Apple needs to send your phrases to its servers to make sense out of your yapping.
But Apple also stores your messages for an unspecified amount of time when you use Dictation on your iPad. ZDNet notes that though Apple is upfront with what they're doing (there are clear warning prompts), Apple is still unclear on why they're doing it. Specifically, the words and phrase Apple uses—'information like', 'your device will also send Apple other information' and 'Older voice input data that has been disassociated from you may be retained for a period of time'—is incredibly vague.
Of course it's not like Apple is going to use your voice messages against you or something. Apple is collecting data to improve Siri and Dictation. But it's important to remember, especially if you work in a sensitive workplace, that Apple will store your dictations on its servers and once they're on its servers, they pretty much belong to Apple at that point.