[From Firebird]
The major Firebird version currently in development is v.2.5. Its feature set is being finalized at the moment in preparation for entering the Beta stage of development. The start of the Beta cycle will be accompanied by a “feature freeze” rule.
The v.2.5 cycle has presented more challenges than usual in the areas of debugging and testing, due to more significant technological rework in the multi-threading part than we expected. The effect has been some degree of slippage from the original schedule.
The article continues at
http://www.firebirdsql.org/index.php?op=devel&sub=engine&id=roadmap_2009&nosb=1