Hi Abhijit,
WELCOME to SCN! 
My query: Can SAP HANA certified consultant be hired for SAP BI role ( considering very few companies implementing HANA)
---Definitely YES..As I have said above, SAP HANA is also BW..You just changed your database to HANA database to make BW faster..Plus, you also have another user interface for developing objects like SAP HANA STUDIO instead of the SAP LOGON pad..All of your knowledge in BW can also be used in HANA development..
However, the certification is just an additional points for your application..You really need to understand the concepts in order for you to be hired..
If you are already used with SAP BW in HANA, don't worry in shifting to SAP BW not in HANA since they are just sort of similar..
Regards,
Loed