Bob it does future PAS transitions, or at least did last time I looked.
You can enter the date of transition and to decide on the level of PAS attained you'll need to download the PDF of this years pay review.
Total up your pre transition pay, basic and flying pay and look for the nearest PA level that doesn't reduce your pay. Work out how many full years you'll serve as PA and add to your start level and hey presto that's the level you'll leave in or pension purposes.
Caution all the above may not be true!