Hi Pradeep,
I followed up with SRM colleagues and received this in response:
"Thanks for your question. Ariba is not replacing SRM. The release of a new enhancement package for SAP SRM (EHP 4 for SAP Supplier Relationship Management 7.0) is planned for Q1 2016 and subsequently further developments via the Customer Connection program."
(Q1 2016 date is current plan and subject to change)
FYI, in addition, the Ariba team is working on updating their roadmap content in Jan 2016.