You could look through language ratings like this https://www.tiobe.com/tiobe-index/ https://www.tiobe.com/tiobe-index/ And choose some new language which is

You could look through language ratings like this https://www.tiobe.com/tiobe-index/ https://www.tiobe.com/tiobe-index/ And choose some new language which is not loosing its market share (like Java, PHP or Perl), but growing now (like Python, Go). Also the best way to switch to new language - is to choose some similar language to the one you used recently, like PHP -> Python or Python -> Go. Anyway, good luck in your career!