I have no idea what sales are like. The closest I can come is to use the product selector to the left of the page here to get an estimate of the fraction of the questions that are asked about Simulink. However that does not necessarily tell us anything more than the fraction studying in university since quite a large portion of questions here are from university students.
I have no idea how universities and industry decide whether to ask questions here or not. I know that the largest university in my province teaches MATLAB but I have never seen anyone there ask a question here, or contact me. A few days ago I noticed a research/industrial company in my city that advertises offering MATLAB solutions (among others) but I had never heard of them or any of their employees before. And people in markets like automotive never seem to ask questions here, other than perhaps a very small number of questions about the CAN blocks. So I don't think we can actually use the questions here to understand the demands in the wild.
Personally the only use I have had for Simulink has been to answer questions about Simulink. But that more tells you that I grew up in the procedural language side and never happened to work in simulation or model based design. I have also never happened to work in Game development, or graphic design, or any of a large number of other large fields, so that's a "I wouldn't know" rather than a "those are small and unimportant"
I think we would need to know more about what your organization produces to give better opinions...
