Betas are not planned. Every beta may become a release.

Alpha - we know there are bugs, and we know some features are not added/complete yet.

Beta 1 - we know there're bugs, but we think we won't be adding any new features.

Beta 2, 3, 4, 5, etc - we think there're some bugs left, but we don't see any and want the community to take a look.

RC - we can't find any bugs, community didn't report any bugs for the last Beta.

Release - either no bugs left and nobody found them.