If you have chosen to become a Tableau developer then you are on the right path. Because if you will look at the current market situations, then you will find Tableau has a very good career. But the future of anything can not be predicted the future of Tableau as it is just a visualization tool and there might be a chance that many more tools can come in the future and they might replace Tableau, but for now and in further 3-5 years Tableau is not going anywhere. For becoming a successful Tableau developer you must add some more skills in addition to Tableau will give you good career growth like R, Python, Predictive analytics, etc.
To prepare for Tableau Interview go through Tableau Interview Questions and learn about Tableau from top experts. Enroll in Tableau Course to get expert guidance.
I am also mentioning a video tutorial for you which you must watch to learn more about Tableau.