Why? OEB had a C check in August so why hurry and get rid of it might as well use up the two years.
That was August 2016 so I expect OEB will depart August 2018 - just as the second batch of four B787's arrive to fly out of the Brisbane base.
The only way that OEB could remain in service after then would be if it was given its fourth "D" check - a very expensive option so I don't think that will happen. OJS/T/U are coming up to their third "D" check and, in the case of "S", they gave it a "C+" check which bought another two years. The rumour mill indicates that the six ER's will get their third "D" check and remain in service until 2025 (after the A380's are retired) and also, OJU may get a "D" check to keep an extra aircraft available as well as keeping the simulator(s) acceptable with their RR engine configuration.
I don't expect there to be a RIN for the B747 crews as the aircraft will be around for a long time yet and attrition will take care of the small reduction in hulls.