It seems like you have to solve each problem as it comes up and not worry too much about the future. There will always be options for solving the next problem and the folks on this board will be happy to help give you you ideas for dealing with each stage.
I guess what I wonder about most is if he is happy with the older kids in the classes he is already in. Do they seem like a better social fit than in the younger grade? Is he accepted by them and allowed to participate?
I also know that you have many other kids in the household and I would want to make sure that his skipping wouldn't painfully disrupt another kid's status in his/her world. If this might be a problem, I would try to address it before the skip and see if there are ways to minimize any disruption.
I was skipped out of a class that I loved into a class that shunned me so I am very cautious about the social aspects of a skip. But it sounds like he may be being eased into the new situation more seamlessly than I was and I suspect that makes a big difference.
