Listen, I don't mean to sound pessimistic, but... you see there's no need for legislation here; it's a civil service change, which was already announced last year. The time difference between the announcement of citizenship ceremonies and the first one was only a few months. In fact, they began so quickly that many localities had to scramble to figure out how to comply with the new requirements. The hold up on the exam was that the subject matter had to be determined and test centers decided. We know that they've done most of the work for the former, and we're in the dark about the latter. But it wouldn't surprise me if the announcement of exams was soon. After all, I filed in July and then like 3 weeks later, they overnight introduced the requirement that you had to show proficiency in English or Welsh. I'm not sure how they test this, but they got the system going very quickly.
The thing about the UK and Europe is that change seems to take a long time, but when all the gears ahve been set in motion, then it happens as rapidly here as in the states. The talk about the Euro went on for years. But the system changed practically 100% in a matter of months.
You might not have to take the exam, but this might only be by a matter of weeks, not months.