I think that if he is so intent on killing he may simply move the area a little wider rather than change his victim type.
I think unless you walk the streets pulling tricks you should be safe enough.
He does seem to be quite smart, the worst thing is, the smartest thing now would be to stop for a few weeks and wait for the Police hunt to die down and the Druggie Prostitutes to venture back on the streets.
I dout they'll learn, it's drug and alcohol money they're after so if you need a fix you need to work.....
Very difficult times in Ipswich and I feel for the area.
My Bessie Mate lived in Ipswich for 5 years now in Cambridge so I know the area's they're on about.