And the future is... ?
You are right to be cautious. This term your school will carry out a review of staffing arrangements ahead of the new rewards structure that sees management points disappear and teaching and learning responsibility allowances introduced. It already seems clear that some schools are looking at whether pastoral posts can be paid TLRs. So, whatever you are paid will only be for one term and then what you will earn will be subject to the outcome of the review. Your basic salary will be safeguarded on the main scale and any post threshold points, but you might no longer receive any or some of your extra responsibility allowances. You might decide you don't want to take on the responsibility in view of the uncertainty.