Currently, we do not have any near-term plan of translating Mentimeter site into more languages. This is mainly because you can now input your content (questions, answer options, bullet points, etc) in any language that you are comfortable with.
If you'd like to see Mentimeter translated into another language in our future development, feel free to head over to our product forum at http://mentimeter.uservoice.com/ to send in your recommendation! We will take it into consideration in our product roadmap. 😃