On June 13 2008, the new Informix version IDS 11.50.XC1 (Cheetah 2) was released for SAP products based on the kernels 46D_EXT, 46D_EX2, 640, and 640_EX2. This includes, for example, SAP R/3 4.6C, SAP R/3 Enterprise 4.7, SAP Netweaver 2004, and SAP Business Suite 2004.
UPDATE May 22 2009: We have now certified Fixpack 4 (XC4).
For more information, see SAP Note 1176689 and the Product Availability Matrix (SAP Service Marketplace login required).
(14 November 2009)