Mauricio Fernandez reports that the next minor version of Ruby, Ruby 1.8.5, is due for release in mid August to coincide with the Japanese holiday of Obon. Ruby releases are usually tied to holiday periods, most notably Christmas for 1.8.3 and 1.8.4.

For the more adventurous, the initial preview release of 1.8.5 is coming by the end of June, with other preview releases in July and August. If Japanese is your thing, there's more info here.