IPSOS and GFK did not merge. GFK sold four of its divisions to IPSOS: Customer Experience, Experience Innovation, Health and Public Affairs. GFK still exists in its own right and continues in the marketing business - and competes with IPSOS outside of those businesses which it sold to IPSOS.
OK, thanks for the clarification. The email I got from them calls it a merger but is very precisely worded to mention only shopping, with no indication that GfK will still continue as an independent company.