btw, I was fooling around with Qubes 4.0rc2 for about 10 hours today, as I was eager to leverage the new HVM flexibility regarding PCI assignments.
it behaves rather buggy / crashy at this point in time.
I think its fair to say that RC2 will not be the final RC ... and 4.0 final will probably not ship this year.
So continue sticking with 3.2 for now, will be supported till end of 2018.
note to self: use a different ssd next time

going to spend the weekend reinstallingl 3.2
EDIT: restoring qubes backups was relatively painless, altough I am left dumbstruck by some braindead-ish issues that the Devs have not yet ironed out:
1) could not restore/overwrite fedora-23 and debian-8 templates ... which means alls AppVMs based on those templates were broked (wrong kernel, firefox version....)
2) most dom0 settings got lost (AEM!!!, wifi passwords, wwan/umts connection profiles, crontabs, /etc/qubes*)
on the plus side ... I have stumbled upon a way to make the Touchscreen work via dom0 while keeping WWAN functionality in sys net ... info added to first post:
@reboot /usr/bin/sudo /usr/bin/bash -lc 'sleep 3; export DISPLAY=:0.0; echo 0000:00:1d.0 > /sys/bus/pci/drivers/pciback/unbind; sleep 1; echo 0000:00:1d.0 > /sys/bus/pci/drivers/ehci-pci/bind; sleep 1; /usr/bin/xinput set-int-prop "Fujitsu Component USB Touch Panel" "Evdev Axis Calibration" 32 918 15776 637 14913'