Thanks for taking action. Did a quick check yesterday evening with basic core, seems ok.
However as you already mentioned, most of the modules using jQuery (incl. my own ones) will not work out of the box when upgrading the files to latest jQuery version.
Guess it's better to stick with the actual version to keep backwards compatibility with existing modules for the 2.8.x series (or add the jquery-migrate script as you suggested and run further tests on existing modules before final 2.8.4 release).