The United States Citizenship and Immigration Services (USCIS) announced on May 3, 2017 that it completed data entry of all fiscal year 2018 H-1B cap-subject petitions selected in its computer-generated random selection process, and that it began returning all H-1B petitions that were not selected.
The agency did not provide a definite time frame for returning these petitions, but the unselected FY 2017 H-1B petitions were returned by the end of June 2016. The same timetable seems likely this year.
Petition approvals for selected cases have already started being sent. Because of the large volume, processing times vary greatly and petition approvals are likely to continue through the summer and even into the early fall, as was the case in prior years.
For the full text of the USCIS announcement can be found at the USCIS website.