Hi,
I would say BI knowledge is not required to learn HANA until and unless you are going to work on HANA on BW project
Get the knowledge of BODS as it is going to be used for replicating data into HANA and especially if its Big Data and Unstructured data
You can also learn BOBJ as Ravi mentioned as it would be used for reporting
Leaning SAP Lumira will also be helpful
As a HANA Consultant i would also like to mention one more thing that in HANA SPS5 SAP introduced XS Engine to create light weight Web Applications and its now a very important part of HANA and to learn this - you need to know JSON, JavaScript, OData, SAP UI5, JQuery and HTML5
It might be better if you learn ABAP ON HANA : for this also you will find info in my blog
To learn more about HANA, check my blog :
You can also know more about HANA and ABAP On HANA in the OpenSAP online course being conducted free by SAP :