> How far have releases been apart in the past?

2.0 - June 2008
2.1 - September 2008
2.2 - December 2008
2.3 - August 2009
2.4 - October 2009

That is 3, 3, 8 and 2 months in between, 4 months on average. That means MorphOS 2.5 is overdue ;-)