That paper, due in January, will explore in greater detail some of the issues flagged up by the Green Paper - in particular, exactly how the system of assessment and performance-related pay might work.
Meanwhile, teachers could be forgiven for reading between the lines to try to work out what the Green Paper really means and just what they will be expected to do to join the higher pay scale.
But despite the lack of details the Green Paper makes it clear that teachers would be expected to "extend learning opportunities for pupils" and "undertake a significant amount of training outside school time".
These demands are in addition to fast-track trainees, who will have to forgo up to six weeks holiday a year for training or industrial placements.
At present, many teachers are paid extra for running homework clubs or training out of hours, and that would continue. But the paper suggests that senior teachers might pay more towards doing Masters or PhDs. Younger teachers might qualify for help with the cost of further study.
Tories called it a "sleight of hand" that was scarcely the reward for excellence the rhetoric pledged. Unions say it raises equal opportunities problems.
Doug McAvoy, general secretary of the National Union of Teachers, warned:
"Governors may use their flexibility to pay staff, but people with childcare responsibilities will be disadvantaged. We will be against it."
The NUT plans to consult members before delivering a full verdict. But a week spent studying the Green Paper has not lessened its opposition to PRP and its potential to divide staffrooms.
The National Association of Schoolmasters Union of Women Teachers puts on a more positive front but also says serious questions need to be answered about appraisal and the power of governors and heads to set pay.
Nigel de Gruchy, NASUWT general secretary, warned against people with similar appraisals receiving considerably different salaries. Consequently,the role of the external assessor will be a crucial factor in overseeing schools' appraisal systems and reviewing each case where a teacher crosses the pay threshold.
"We will have to be careful not to overload schools with bureaucracy," Mr de Gruchy said. "They will have to cut back on OFSTED inspections or target setting."
That could prove an important crux - how bureaucratic will the appraisal system be? And will the number of teachers crossing the threshold be rationed?
Officially, ministers say no and are committed to a budget of more than Pounds 1 billion and a continually increasing wage bill to bring more than half of teachers over the threshold. Although that would mean more than 200,000 teachers on the higher scale, they expect to appoint only 200 to 300 external assessors across England, which in itself could act as a brake.