One of the most fascinating things about working on a trading floor is that models such as BSM transcend their normative aspect and become mental models. Pricing an option? Basically only two things matter: where the underlying asset forward price is at maturity (this is related to the concept of drift) and what the volatility is. At any time, your job is choose “bumps” (which you add to market prices) in order to maximize your odds of making money on a trade subject to beating your competition on price. There are some people who make a living making these markets who likely have never heard of “Ito’s lemma” or diffusion equations.
Still very much present, it powers "SecDB" (which is pretty much the nervous system of the entire markets business). While there's certainly been openness to Python/etc and tech to integrate Slang into the 21st century, it's the kind of thing that's hard to imagine ever being phased out.