You "need" to learn several languages and frameworks as part of becoming a reasonably competent programmer.
The more diverse the better, but the exact choices are up to you 
Jack of all trades, master of none. I think such a broad statement leads him in the wrong path. I think he "needs" to learn a single language and master it before he even starts to learn another language and then decide which would be most beneficial to his career. I'm not saying you're wrong, actually you are spot on, I just don't want to see him take on the task of learning multiple languages and once and then end up the guy that nobody wants because he knows a little bit about everything and a whole lot about nothing.
