Second-hand, but still credible information suggests it will be 2 pilot DXB-LHR-DXB unless operational requirements such as Flight time limitations, particularly 30/7, or weather require 3.
The London slips will remain unchanged, with one being 38 hours and one 62 hours to provide "standby" coverage in case of disruptions. At present the patterns starting and finishing in Melbourne have the longer slip in LHR, but that may change as those patterns will have an overnight in Melbourne before and after DXB operation making it an 11 or 12 day pattern.