Azure AD integration now provides multiple approaches direct from Microsoft and the ability to write back to on premises AD. The recently update table on MSDN outline the capabilities, http://msdn.microsoft.com/en-us/library/azure/dn798669.aspx. I'm also particularly keen to monitor the Azure Device Registration Service Preview as this will enable very dynamic environments, http://msdn.microsoft.com/en-us/library/azure/dn788908.aspx.
The new and soon to be updated Azure AD Sync Services (AAD Sync) information is available here, http://msdn.microsoft.com/en-us/library/azure/dn790204.aspx.
Happy sync'ing.