Given your current time frames, in my opinon, you would be crazy to consider going back before Citizenship. Once you have got it, you could TRY going back in order to see if the UK is what you want for your family and if you find it's not then you can return either here or Interstate.
Personally I feel that if you were to go back prior to Citizenship it may well be a decision you live to regret as you will be painting yourself into a corner.
Good luck with the decision, I'm sure it can't be easy, but after 4 years another 6 months wouldn't hurt would it???