Hi Vijay,
If you are going to become Database Developer or Administrator, then learning SQLScript should be enough for you. But learning a bit of XSJS(Server Side JavaScript) will surely be helpful.
But if you want to become Application Developer, then you have to learn Server Side JavaScript, learn about OData and SAPUI5(which requires knowledge of HTML5, CSS, jQuery, Javascript).
Also check my below blog to learn more about HANA:
Want to learn SAP HANA? Where to Start? Certification? Updated 21.09.2014
Regards,
Vivek