Suppose you brine a chicken in a heavy solution e.g. 10% saline. Suppose you now boil this chicken in water which does not contain salt or contains a little salt e.g. 5g. How much of the salt, if any, will come out of the chicken and go into the soup. Will it try to equalise via osmoses and keep putting salt out until an equal concentration is present in chicken and soup or not? If it does, i take it a large amount of salt will ditribute into the soup liquid leaving the chicken less salty?
I'm not exactly sure why you're trying to brine then boil; you should be able to simply boil your chicken in salty stock and get plenty of salt into it. It won't take nearly as long as brining, because things happen faster in boiling water.
Assuming you boil for any significant length of time, much of the salt will indeed come out into the cooking liquid, and you'll end up with your soup approximately as salty as the chicken. (If the chicken is in large pieces, this of course only applies to the part the brining and cooking liquids can actually reach.)