The last WHQL release was Catalyst 14.12 Omega, published on December 9, 2014. Previously AMD released monthly Catalyst updates, this then slipped to quarterly releases in 2013-2014 and now driver development seems to have slowed down even further.
Since the December release, AMD has launched a mere two Catalyst beta drivers and despite several delays fans are still waiting for the promised FreeSync support for multi-GPU configurations.
As TPU notes, this is in stark contrast with NVIDIA. The green team has accelerated its driver update cycle with its Game Ready driver program and issues new WHQL-certified releases before almost every AAA PC game release.
Last week AMD's Roy Taylor promised a Project Cars driver would be out this week but it appears new WHQL drivers aren't expected to be released until the third week of June with the launch of Fiji - over half a year since the last non-beta release!