Wow cedarmoon what a great answer!
As an Aussie with accelerated kids I can say at times it is difficult. They do get bored in class often and I have to really push and be active in their schooling in order to get any accelerated material for them.
In saying that I would absolutely do it all over again! The benefits they get by being given the opportunity to read early and work at a higher and deeper level than average are well worth any pitfalls. In fact if I did it all again I would aim higher! The bigger the gap between where your kid is and where the rest of he the class is the more help the schools will give you! This is particularly true in Australia.
There are many schools in Aus where tall Poppy's are encouraged. Where being a nerd is seen as cool. My kids are in one of these schools. The kids and parents think being smart is great. The school however is mixed on it. (Odd I know!) So when my kids do well they are congratulated and given praise for their hard work not bullied. These days theses school environments are becoming more and more common.
It is far better to be too smart and bored in school than sit in a classroom feeling stupid because all the material goes over your head. At least an early reader when bored can pull out a good book to learn some more from
Don't worry about the future. Teach them now and cross each bridge as you get to it.