Pre-orders and previews begin April 10, launches April 24.
Leaked Image Suggests 'Voice Memo' Will Return in Future iOS 7 Beta Release
Also, a tipster tells us the release notes for the first iOS 7 Beta mention the Voice Memo app:
Voice Memos - Known IssuesThe Voice Memo app doesn't seem to appear in any of the iOS 7 marketing materials on Apple's website, but developers should see it in a future iOS 7 beta release and we expect it to be included in the final iOS 7 release this fall.
The VoiceMemos app is not available in this seed.