If you want to work in the commercial world, get a job - you have a lot of (practical) skills to develop, and people will wonder why you needed another year of coursework before starting work. Consider aiming for a job at a company that's good at an interesting niche, and note that new grads can get hired into many niches. There is such a thing as a junior data scientist, junior security expert, ...! (And there's also such a thing as a web developer working at a robotics company - such a web developer could easily dip a toe into robotics.)

It's not necessarily a bad idea to play around with MOOCs to take a look at other skills while working at your job, but if a university course wasn't enough to make up your mind a MOOC won't be either.

(In general, a thesis or internship is a good way to look deeply into a specific niche. But if you're three months from graduating, I don't think that advice will help you...)