“used to“ implies habitual actions is the past that is not valid now. How about questions “did you use to...?” Could we ask such questions when we want to learn about habits in the past BUT we aren't sure whether those habits are still valid now or not?
You are correct that saying that or asking whether someone "used to" do something implies that the action took place in the past and does not still continue.
If you asked me, "Did you used to work with XYZ?" and I still did, my response would say as much: "Yes, and I still do."
If you want to ask without that implication, use present perfect tense: "Have you worked with XYZ?"
It's also a trick question by implying that a person once did or still does such as "Do you still beat your wife"... the question being that you once did and inferring that you still do. No matter how you answer it with a yes or no. You've just labeled yourself as a wife beater. The proper question would be; "Have you ever..."