If I don't put names down, it's because I believe the current leader of the parties in question will have been kicked out by then.
United States: Barack Obama, D Senate R House
United Kingdom: Labour
Germany: SPD/CDU (Grand coalition)
France: François Hollande, PS Assemblée nationale
Australia: Coalition without control of the Senate
Netherlands: Mark Rutte and his
Denmark majorityDenmark: Helle Thoring-Schmidt, A-F minority
Spain: PSOE + regionalists
Canada: Conservative minority
Italy: PD-led coalition, though the party should be renamed by then
Poland: PO with a SLD opposition
Belgium:Sweden: Håkan Juholt, S minority with MP-V support
Finland: SSP-Kesk-Vihr-RKP coalition (Social Democrats, Centre, Greens, Swedes)
New Zealand: John Key's last mandate (National minority)
Portugal: PS minority
Ireland: Fine Gael coalition, though with whom nobody knows
Greece: PASOK, though party politics will mean little by that point.