the titan x full waterblock will fit the gtx 980 ti according to ekwb's wesite.
NewsJun 2, 2015 Existing EK-FC Titan X compatible with the latest NVIDIA® GeForce® GTX 980 TiEK Water Blocks, Ljubljana based premium water cooling gear manufacturer, is pleased to announce that the existing EK-FC Titan X series water blocks are compatible with reference design NVIDIA® GeForce® GTX 980 Ti officially launched on June 1st 2015.