I think simply being a gifted child isn't enough- they need to have a good work ethic to harnass that vast potential. I don't think they will do alright no matter what- but I can see why so much of our school's resources go for the kids who are below grade level and not above grade level.
That is true about PhDs. There was an interesting thread here a few months ago about having a PhD in Chemistry- apparently that used to be a great job but now that has been largely outsourced to China/India/etc. and there is alot of job insecurity there.
I do think talking to gifted children about the reality of the work world is important.