万事俱备，只欠东风 wànshìjùbèizhǐqiàndōngfēng lacking only one final detail
Everything is ready except for one last crucial factor; literally "all is ready except for the east wind," referring to a story from the [[三国演义|三國演義|san1 guo2 yan3 yi4]] where a fire attack required a specific wind to succeed.