Apple has just issued the 10th developer beta (15A5372a) for iOS 11 and you can download it right now (if you're enrolled for it). Apple doesn't specify if this is the final beta or not. You can download the beta at Apple's Developer site if you're a registered, paying dev or check out Apple's Public Beta site for the 9th public beta released earlier this week. Apple will announce its upcoming iPhone hardware at next week's event (on the 12th) and should release iOS 11 for all users a week after that. Via
Source: http://www.gsmarena.com/apple_issues_ios_11_developer_beta_10-news-27164.php
