As said on the mailing list:
I would like to completely remove Qt 4 from the Ubuntu archive before the 20.04 release. This includes all of KDE 4 and dependencies.
The Debian Qt/KDE Team (which I am a part of) is raising the status of the Qt 4 removal bugs to RC, and since the Qt 6 work is starting upstream in the dev branch in the coming months, now is the time for Qt 4 to go.
My timeline for this is to change all of the bugs filed to ask people to port to removal bugs, and go over the list of Qt 4 reverse dependencies one last time, so the removal can be done at the beginning of the 20.04 cycle before the archive opens. This would make 19.10 the last release with Qt 4.
Flavors, please check if Qt 4 is on your ISO, and if it is, make plans to remove it as soon as you can. Please hop in #ubuntu-qt if you would like help porting your favorite application.