Yes it will payoff. Your ability to code in R combined with the theory in stats will be valuable.
You should learn another language alongside R, it'll make you a more valuable candidate when entering the workforce.
There is no harm in learning another language, and it would be beneficial to go with Python:
1. Python and R are the primary languages listed as a requirement in analytics/data science/stats based jobs
2. Python and R have different but at the same time similar syntax, knowing one makes learning the other easier