| Narukenai |
My suggestion would be Cleric over Druid as a general rule, as a Cleric you still maintain your low level domain powers, domain spells, don't have a concern about losing your divine spells to metal (which is useful if you decide to hike up your AC with a mithral buckler), and don't have as many class features lost overall to your Theurge levels (wildshape, poison immunity, etc.). Furthermore the quicker access to healing spells and the unique Cleric buffs are probably going to serve you better than the few unique Druid spells that you don't have better equivalents to from your Wizard levels.
As for those last four levels my suggestion would be to put them all into Wizard or a prestige class that gives you wizard spellcasting levels, as the high level Wizard spells provide you with some amazing abilities and you will have all your divine bases covered with 7th level Cleric spellcasting (Divine divinations, Heal, Raise Dead, all removals, etc.)
Also as a quick tip there is a trait which grants you a +2 caster level bonus to one caster class up to your total level maximum, taking that in Wizard will help you fill in your power spells a little bit, and taking anything to increase your generic caster level as you go along will help you get the most out of your class spread.