I suspect Matlab will have a long tail in engineering education, for a number of reasons: 1) It's effectively free for educational use thanks to generous site licenses. 2) A lot of curricula have been developed around it. 3) Indisputably, it works.

But outside of academia, let's face it, the most widespread "engineering IDE" is Excel. Relatively few engineers continue to use math and equations after they graduate. A lot of their calculations can be done in Excel, or within their CAD software. The biggest threat to Matlab is the automation of engineering calculations.

As a result, it's more mixed, with the people who are actually doing quantitative work coming from a variety of fields including math and physics, but also from areas that have no prior loyalty to Matlab such as biology and statistics.

For instance in my department, any deeply quantitative work is done by a very small handful of "math people" who may or may not have "engineer" job titles, but whose degrees are in math or the physical sciences.