A more user-friendly, versatile and higher performance language. E.g. Julia can do everything R, Python, Fortran, Matlab and C can do in principle all in one language.

You can use R and Python packages from Julia. You can call Fortran and C code from it. Unlike R and Python you don't need to have a module rewritten to C or Fortran code to get high enough performance.

In fact Julia will often outperform C and Fortran code. There are researchers which have switched from Fortran to Julia to get a higher productivity programming language expecting to get a performance drop only to realize they got a 3x performance increase.

The main downside of Julia is that it is a very new language. R and Python and old and hence well known, but Julia is a rapidly growing and taking over serious areas. Next generation climate models are built using Julia e.g.