Is TeX really used in publishing industry?If I have to learn a typesetting programming language to find a job in publishing industry is TeX a good choice or I should learn something else? I'm also interest if or in which publishing industry is used TeX.
Which type-setting tools is used really depends on the type of publication to be type-set. TeX (in a wider sense) is widely used for scientfic journal and book publications. Since TeX is designed for mathematics, it dominates these areas but many large science publishers rely on TeX as well, Wiley, Elsevier, Springer to give a few examples. The benefits for publishers is that the author will essentially do the type-setting for them and production costs become lower. If you look at book production in general the dominant software will be Adobe Indesign and QuarkXPress. These are not programmable in the same sense but are layout software with graphical interfaces. These software target a different market and are used by the publishing industry where authors provide materials but the layout is done by the publishers.
So the answer to your question depends on what part of the publishing industry you would aim for. In terms of TeX publications, the job will be to generate packages for layouts of publications whereas for the others the job is more one of designing individual layouts for each product. There are other proprietary solutions for specific publishers for which I do not have any insights but I believe the ones mentioned are the major solutions.