With this move, qt also gets updated to 5.9.1, the first bug fix release of the 5.9 series.
It should be safe to answer yes to any replacement question by Pacman. If in doubt or if you face another issue in relation to this update, please ask or report it below.
Most of our mirrors take 12-24h to synchronize, after which it should be safe to upgrade. To be sure, please use the mirror status page to check that your mirror synchronized with our main server after this announcement.