"Fixed in the next release" means that the source of the problem has been identified and a fix has been generated by developers. The next version that is released will include the fix, so when you upgrade, you will automatically get it.
Some fixes have too many or complicated file changes, or require changes to database entries in multiple tables. Sometimes if there a lot of changes, there can be conflicts with changesets for users on different versions or even slightly different code than the development version (which is always a version ahead). More importantly, it is easy for users to make mistakes with complicated changes (in the past when we posted them, many users ended up breaking their sites), so we don't post manual changes for every bug fix.