Police flying is relatively new. With 1 or two exceptions, most Units have existed for a maximum of around 10 years, and some less than that. There is no indciation of major changes in the future, but you can never tell.
Aside from cost of living/inflation increases in pay, there is not much "progression" or scope for expansion/growth in police flying other than to Chief Pilot. These are limited opportunities - most Chief Pilots do not move. The police line pilot's job has many advantages, but one of its drawbacks is you are in the same place doing the same work. Some helicopter pilots like a variety of work and change of scene.