Ubuntu 12.04 hasn't been released yet, but Canonical is already planning Ubuntu 12.10 and an initial release schedule draft has been published on the Ubuntu wiki.
Ubuntu 12.10 Quantal Quetzal will have 3 alpha versions, 2 betas and just like Precise, no release candidate. Here's the Ubuntu 12.10 release schedule:
- Alpha 1 - June 7th
- Alpha 2 - June 28th
- Alpha 3 - July 26th
- Beta 1 - September 6th
- Beta 2 - September 27th
- Final Ubuntu 12.10 release - October 18th