Ubuntu 15.04, which is codenamed the Vivid Vervet, is currently penciled in to release on 23rd April, 2015. The release date for Ubuntu 15.04 has now been firmed up as are the other development milestones leading up to the mid-April debut of this release. Ubuntu 15.04 a big focus on convergence and Unity 8 with Mir, earl
y systemd integration, and many other changes planned for development over the next six months.

December 18th	Alpha 1 (Not Public Release - opt-in)
anuary 22nd	Alpha 2 (Not Public Release - opt-in)
February 28th	Beta 1 (Not Public Release - opt-in)
March 26th	Final Beta
April 16th	Release Candidate
April 23rd	Final Release