The wheels are turning on the third and final phase of the Productivity Commission's review of superannuation, one that will tread once more well-worn terrain over models for default allocation of savings and the relative return of non-for-profit versus bank-run funds.The treasurer, Scott Morrison, on Friday set out terms of reference for a "system wide review" by the commission. These build on the commission's two earlier reports in 2016 on efficiency and default models.Morrison said the government asked the Productivity Commission to complete the review within 12 months and sketch out "the early provision of the evidence base for future reforms to the superannuation system." January 2018 is the target date for a final report.The assessment "should be based on the five system-level objectives, 22 assessment criteria, and 89 corresponding indicators set out in the Commission's Stage 1 report," Morrison said."This will be the third and final stage of the review," he said.The Productivity Commission last year said it "identified vertically and horizontally integrated businesses, often owned by banks, as one of the main barriers to entry that can give rise to uncompetitive incumbency advantages in the superannuation industry."In an issues paper in March on alternative default models for superannuation, the commission, maybe with resignation, said "the Inquiry has managed to unite the superannuation industry against the Inquiry's potential contemplation of more-than-incremental reform."A healthy dose of scepticism would suggest that there must be rents to be recovered for the benefit of members for such unanimity to be valid."