H1-b after 6 years exhaust, without gc filing

[Trango]

My H1-B visa will be expiring in mid-April 2018 and will be exhausting all 6 years (including all external stays). Thanks to last minute chaos but my employer hasn't filed for Green Card this time. Can I be eligible for fresh H1-B case in April'2019 if I travel in mid April'2018 or should I leave USA by end of March'2018 itself for the cycle to reset for 365 days?