As Jeanne says, try sites like Monster to see what kind of market there is for OSB. But if you're choosing between either OSB or Big Data, I'd be inclined go for Big Data, as it will be much more broadly applicable and (hopefully) more useful in future. Obviously Java and Hadoop are closely linked, but you could also look at free training in things like MongoDB, or work through relevant books/tutorials. You'll need to put some work into understanding the benefits and limitations of different approaches to Big Data, as well as perhaps looking more broadly at data analysis or data mining e.g. via Coursera or Udacity (free online courses) or the IBM-sponsored Big Data University.
If you're looking at proprietary data-related technologies, there are lots of jobs at the moment for people with "business intelligence" skills e.g. using tools like OBIEE, but this is still a proprietary market and there is a risk of ending up in a bit of a cul-de-sac.