Hi Srinivas,
Srinivas M wrote:
1. Having experience in Siebel learning SAP HANA is it a right decision?
There is CRM on HANA which is quite promising. Please refer to the following links to get more details.
http://scn.sap.com/community/crm/blog/2013/03/07/crm-on-hana-is-reality-for-business-users-at-sap
http://wiki.sdn.sap.com/wiki/display/CRM/SAP+CRM+on+SAP+HANA+Cookbook
2. Is it sufficient if I learn SAP HANA and SAP BO for present trends? Can I survive in realtime by having these two technologies as 2 yrs. SAP BI & SAP HANA experienced guy?
SAP HANA is an evolving technology with multiple use cases and application coming on board. The scope is quite vast and so would be the demand. There is more to SAP HANA than just HANA and BO, hence I would recommend to decide something which is your core domain (CRM) and build the skill set around it.
3. what is the expected scope for SAP HANA and SAP BI for down the line 10 yrs.?
3 years back I didn't even know that something like HANA would exist 
, so 10 years is a pretty long time. Don't think that far in future. But the immediate future looks bright for HANA.
4. Why cant I go for Informatica & OBIEE why should I choose SAP HANA & SAP BI in terms of market scope and job opportunities?
Sorry, no idea about Informatica and OBIEE, so can't comment on this.
Regards,
Ravi