Hi Nitin,
If you plan to upgrade BPC Backend to SP11, then you should update the EPM Add-in to SP15. It will ensure version consistency.
You can check BPC 10 NW SP11 Central Note : http://service.sap.com/sap/support/notes/1826720
You must update the SAP BusinessObjects EPM Solutions add-in for Microsoft Office to SP15 for use with this release of Planning and Consolidation. We recommend that you install all components at the same time to ensure version consistency.
Thanks,
Ridwansyah