I left the finance industry 3 years ago, so I don't know what the trend is now. But at the banks and insurance companies I worked before, APL was indeed a heavily used language. Usage didn't seem to shrink or grow; it was mostly stable. There didn't seem to be a trend in moving away from it for either life insurance statistical operations nor for back office stuff at the bank (valuation of derivatives etc).

Note that APL was not the predominant language though; that was COBOL and PL/I.