My dd skipped a "bridge" year as well. 5th is the last year of elementary here as it sounds like it would habe been for your ds, Grinity.
I know that the IAS says that those aren't good years to skip, but my dd had no trouble with it at all. She was still at the top of the grade academically and still got straight As post-skip, but she did have to work a little in some of the subjects (especially math), which was good. I guess that it will vary from child to child and will depend on a whole host of circumstances. I wouldn't rule out a skip later, though, if the child seems very advanced in all subjects.
