Python is definitely not the de facto choice. Python and R both have strengths and weaknesses, and relative use depends quite a bit on community. A few recent surveys (http://blog.revolutionanalytics.com/2014/01/in-data-scientis..., http://www.kdnuggets.com/2013/10/rexer-analytics-2013-data-m..., http://blog.revolutionanalytics.com/2013/09/top-languages-fo...) show strong growth for both R and python, and I expect that will continue in the future. There's no reason to limit yourself to one language, and knowing both R and python can only help. That said, you do need to be carefully about spreading yourself too thin, and you want to make sure you're an expert in at least one data analysis environment.