I think learning new martial arts is incredibly important to your growth as a martial artists. Even just learning new styles in your art if you're doing something like Kung Fu where each style is practically a different art is a great way to learn new approaches and skills. I mean, that's basically how MMA started.
Studying contrasting arts is good too. I study/have studied Kung Fu and Capoeria which are pretty darn different, and I think I've been able to take different parts of each to the other to improve my style ^^