Yep - but there is already a system in place for people with exit dates before 1 Apr 07 (£50k gross/£30k net). If your exit date is 1 Apr 07 or later you will currently get nothing for staying in, if I recall correctly.
Although we all know that if you work it out you will be much better off in the long run if you leave, there is a big temptation for people to take the easy option of do nothing - get 30 grand in your bank account.