Yes, it will be a normal ispconfig update. The new 3.1 version is fully downwards compatible with 3.0.5.x.
i git clone over debian8 & ispconfig 3.0.5.4p8 AND on fresh VM install ubunti 15.10. non able to pass login page. on log it wrote admin logged
Strange, it works here on my test server, but my server has been updated for some time. I'lls etup a fresh system the next days.