Looking at the time schedules of the European parties for the EP elections, I could find some indications on the planned timing:
European Liberals and Democrats
According to to a press release from April, "[t]he final ELDR electoral programme will be adopted by the ELDR Congress on 30 and 31 October 2008."
After the public consultations for the PES manifesto have ended, consolidation work is now under way. The manifesto-page tells: "The PES manifesto will be adopted by the PES Council - a mini-Congress with voting representatives from all member parties - in December 2008."
Although I did not find any specific hints, the general schedule suggests that it might be decided at the party's Council meeting from 10-12 october 2008 in Paris.
European People's Party
I did not find any indication for the EPP schedule. (Anyone else?)
Under the category "Tracking: EP elections 2009" am following up national and European activities on the path to the European Parliament elections 2009. So far: (2), (1).